# Executive Summary
The Guideline for Isolation Precautions: Preventing Transmission of Infectious Agents in Healthcare Settings 2007 updates and expands the Guideline for Isolation Precautions in Hospitals. The following developments led to revision of the 1996 guideline:
1. The transition of healthcare delivery from primarily acute care hospitals to other healthcare settings (e.g., home care, ambulatory care, free-standing specialty care sites, long-term care) created a need for recommendations that can be applied in all healthcare settings using common principles of infection control practice, yet can be modified to reflect setting-specific needs. Accordingly, the revised guideline addresses the spectrum of healthcare delivery settings. Furthermore, the term "nosocomial infections" is replaced by "healthcare-associated infections" (HAIs) to reflect the changing patterns in healthcare delivery and difficulty in determining the geographic site of exposure to an infectious agent and/or acquisition of infection. 2. The emergence of new pathogens (e.g., SARS-CoV associated with the severe acute respiratory syndrome , Avian influenza in humans), renewed concern for evolving known pathogens (e.g., C. difficile, noroviruses, community-associated MRSA ), development of new therapies (e.g., gene therapy), and increasing concern for the threat of bioweapons attacks, established a need to address a broader scope of issues than in previous isolation guidelines. 3. The successful experience with Standard Precautions, first recommended in the 1996 guideline, has led to a reaffirmation of this approach as the foundation for preventing transmission of infectious agents in all healthcare settings. New additions to the recommendations for Standard Precautions are Respiratory Hygiene/Cough Etiquette and safe injection practices, including the use of a mask when performing certain high-risk, prolonged procedures involving spinal canal punctures (e.g., myelography, epidural anesthesia). The need for a recommendation for Respiratory Hygiene/Cough Etiquette grew out of observations during the SARS outbreaks where failure to implement simple source control measures with patients, visitors, and healthcare personnel with respiratory symptoms may have contributed to SARS coronavirus (SARS-CoV) transmission. The recommended practices have a strong evidence base. The continued occurrence of outbreaks of hepatitis B and hepatitis C viruses in ambulatory settings indicated a need to re-iterate safe injection practice recommendations as part of Standard Precautions. The addition of a mask for certain spinal injections grew from recent evidence of an associated risk for developing meningitis caused by respiratory flora. 4. The accumulated evidence that environmental controls decrease the risk of lifethreatening fungal infections in the most severely immunocompromised patients (allogeneic hematopoietic stem-cell transplant patients) led to the update on the components of the Protective Environment (PE). 5. Evidence that organizational characteristics (e.g., nurse staffing levels and composition, establishment of a safety culture) influence healthcare personnel adherence to recommended infection control practices, and therefore are important factors in preventing transmission of infectious agents, led to a new emphasis and recommendations for administrative involvement in the development and support of infection control programs.
6. Continued increase in the incidence of HAIs caused by multidrug-resistant organisms (MDROs) in all healthcare settings and the expanded body of knowledge concerning prevention of transmission of MDROs created a need for more specific recommendations for surveillance and control of these pathogens that would be practical and effective in various types of healthcare settings.
This document is intended for use by infection control staff, healthcare epidemiologists, healthcare administrators, nurses, other healthcare providers, and persons responsible for developing, implementing, and evaluating infection control programs for healthcare settings across the continuum of care. The reader is referred to other guidelines and websites for more detailed information and for recommendations concerning specialized infection control problems.

# Parts I -III: Review of the Scientific Data Regarding Transmission of Infectious Agents in Healthcare Settings
Part I reviews the relevant scientific literature that supports the recommended prevention and control practices. As with the 1996 guideline, the modes and factors that influence transmission risks are described in detail. New to the section on transmission are discussions of bioaerosols and of how droplet and airborne transmission may contribute to infection transmission. This became a concern during the SARS outbreaks of 2003, when transmission associated with aerosol-generating procedures was observed. Also new is a definition of "epidemiologically important organisms" that was developed to assist in the identification of clusters of infections that require investigation (i.e. multidrugresistant organisms, C. difficile). Several other pathogens that hold special infection control interest (i.e., norovirus, SARS, Category A bioterrorist agents, prions, monkeypox, and the hemorrhagic fever viruses) also are discussed to present new information and infection control lessons learned from experience with these agents. This section of the guideline also presents information on infection risks associated with specific healthcare settings and patient populations.
Part II updates information on the basic principles of hand hygiene, barrier precautions, safe work practices and isolation practices that were included in previous guidelines. However, new to this guideline, is important information on healthcare system components that influence transmission risks, including those under the influence of healthcare administrators. An important administrative priority that is described is the need for appropriate infection control staffing to meet the ever-expanding role of infection control professionals in the modern, complex healthcare system. Evidence presented also demonstrates another administrative concern, the importance of nurse staffing levels, including numbers of appropriately trained nurses in ICUs for preventing HAIs. The role of the clinical microbiology laboratory in supporting infection control is described to emphasize the need for this service in healthcare facilites. Other factors that influence transmission risks are discussed i.e., healthcare worker adherence to recommended infection control practices, organizational safety culture or climate, education and training.
Discussed for the first time in an isolation guideline is surveillance of healthcare-associated infections. The information presented will be useful to new infection control professionals as well as persons involved in designing or responding to state programs for public reporting of HAI rates.
Part III describes each of the categories of precautions developed by the Healthcare Infection Control Practices Advisory Committee (HICPAC) and the Centers for Disease Control and Prevention (CDC) and provides guidance for their application in various healthcare settings. The categories of Transmission-Based Precautions are unchanged from those in the 1996 guideline: Contact, Droplet, and Airborne. One important change is the recommendation to don the indicated personal protective equipment (gowns, gloves, mask) upon entry into the patient's room for patients who are on Contact and/or Droplet Precautions since the nature of the interaction with the patient cannot be predicted with certainty and contaminated environmental surfaces are important sources for transmission of pathogens.
In addition, the Protective Environment (PE) for allogeneic hematopoietic stem cell transplant patients, described in previous guidelines, has been updated.

# Tables, Appendices, and Other Information
There are several tables that summarize important information: 1. a summary of the evolution of this document; 2. guidance on using empiric isolation precautions according to a clinical syndrome; 3. a summary of infection control recommendations for category A agents of bioterrorism; 4. components of Standard Precautions and recommendations for their application; 5. components of the Protective Environment; and 6. a glossary of definitions used in this guideline.
New in this guideline is a figure that shows a recommended sequence for donning and removing personal protective equipment used for isolation precautions to optimize safety and prevent self-contamination during removal.

# Appendix A: Type and Duration of Precautions Recommended for Selected Infections and Conditions
Appendix A consists of an updated alphabetical list of most infectious agents and clinical conditions for which isolation precautions are recommended. A preamble to the Appendix provides a rationale for recommending the use of one or more Transmission-Based Precautions, in addition to Standard Precautions, based on a review of the literature and evidence demonstrating a real or potential risk for person-to-person transmission in healthcare settings.The type and duration of recommended precautions are presented with additional comments concerning the use of adjunctive measures or other relevant considerations to prevent transmission of the specific agent. Relevant citations are included.

# Pre-Publication of the Guideline on Preventing Transmission of MDROs
New to this guideline is a comprehensive review and detailed recommendations for prevention of transmission of MDROs. This portion of the guideline was published electronically in October 2006 and updated in November, 2006 (Siegel JD, Rhinehart E, Jackson M, Chiarello L and HICPAC. Management of Multidrug-Resistant Organisms in Healthcare Settings (2006) (/)), and is considered a part of the Guideline for Isolation Precautions. This section provides a detailed review of the complex topic of MDRO control in healthcare settings and is intended to provide a context for evaluation of MDRO at individual healthcare settings. A rationale and institutional requirements for developing an effective MDRO control program are summarized. Although the focus of this guideline is on measures to prevent transmission of MDROs in healthcare settings, information concerning the judicious use of antimicrobial agents is presented since such practices are intricately related to the size of the reservoir of MDROs which in turn influences transmission (e.g., colonization pressure).
There are two tables that summarize recommended prevention and control practices using the following seven categories of interventions to control MDROs: administrative measures, education of healthcare personnel, judicious antimicrobial use, surveillance, infection control precautions, environmental measures, and decolonization.
Recommendations for each category apply to and are adapted for the various healthcare settings. With the increasing incidence and prevalence of MDROs, all healthcare facilities must prioritize effective control of MDRO transmission. Facilities should identify prevalent MDROs at the facility, implement control measures, assess the effectiveness of control programs, and demonstrate decreasing MDRO rates. A set of intensified MDRO prevention interventions is presented to be added 1. if the incidence of transmission of a target MDRO is NOT decreasing despite implementation of basic MDRO infection control measures, and 2. when the first case(s) of an epidemiologically important MDRO is identified within a healthcare facility.

# Summary
This updated guideline responds to changes in healthcare delivery and addresses new concerns about transmission of infectious agents to patients and healthcare workers in the United States and infection control. The primary objective of the guideline is to improve the safety of the nation's healthcare delivery system by reducing the rates of HAIs.

# Part I: Review of Scientific Data Regarding Transmission of Infectious Agents in Healthcare Settings

# I.A. Evolution of the 2007 Document
The Guideline for Isolation Precautions: Preventing Transmission of Infectious Agents in Healthcare Settings 2007 builds upon a series of isolation and infection prevention documents promulgated since 1970. These previous documents are summarized and referenced in Table 1 and in Part I of the 1996 Guideline for Isolation Precautions in Hospitals 1 .
Objectives and methods The objectives of this guideline are to 1. provide infection control recommendations for all components of the healthcare delivery system, including hospitals, long-term care facilities, ambulatory care, home care and hospice; 2. reaffirm Standard Precautions as the foundation for preventing transmission during patient care in all healthcare settings; 3. reaffirm the importance of implementing Transmission-Based Precautions based on the clinical presentation or syndrome and likely pathogens until the infectious etiology has been determined (Table 2); and 4. provide epidemiologically sound and, whenever possible, evidence-based recommendations.
This guideline is designed for use by individuals who are charged with administering infection control programs in hospitals and other healthcare settings. The information also will be useful for other healthcare personnel, healthcare administrators, and anyone needing information about infection control measures to prevent transmission of infectious agents. Commonly used abbreviations are provided on page 11 and terms used in the guideline are defined in the Glossary (page 137).
Med-line and Pub Med were used to search for relevant studies published in English, focusing on those published since 1996. Much of the evidence cited for preventing transmission of infectious agents in healthcare settings is derived from studies that used "quasi-experimental designs", also referred to as nonrandomized, pre-post-intervention study designs 2 . Although these types of studies can provide valuable information regarding the effectiveness of various interventions, several factors decrease the certainty of attributing improved outcome to a specific intervention. These include: difficulties in controlling for important confounding variables; the use of multiple interventions during an outbreak; and results that are explained by the statistical principle of regression to the mean, (e.g., improvement over time without any intervention) 3 . Observational studies remain relevant and have been used to evaluate infection control interventions 4,5 . The quality of studies, consistency of results and correlation with results from randomized, controlled trials when available were considered during the literature review and assignment of evidence-based categories (See Part IV: Recommendations) to the recommendations in this guideline. Several authors have summarized properties to consider when evaluating studies for the purpose of determining if the results should change practice or in designing new studies 2,6,7 .

# Changes or clarifications in terminology.
This guideline contains four changes in terminology from the 1996 guideline:
- The term nosocomial infection is retained to refer only to infections acquired in hospitals. The term healthcare-associated infection (HAI) is used to refer to infections associated with healthcare delivery in any setting (e.g., hospitals, longterm care facilities, ambulatory settings, home care). This term reflects the inability to determine with certainty where the pathogen is acquired since patients may be colonized with or exposed to potential pathogens outside of the healthcare setting, before receiving health care, or may develop infections caused by those pathogens when exposed to the conditions associated with delivery of healthcare. Additionally, patients frequently move among the various settings within a healthcare system 8 .
- A new addition to the practice recommendations for Standard Precautions is Respiratory Hygiene/Cough Etiquette. While Standard Precautions generally apply to the recommended practices of healthcare personnel during patient care, Respiratory Hygiene/Cough Etiquette applies broadly to all persons who enter a healthcare setting, including healthcare personnel, patients and visitors. These recommendations evolved from observations during the SARS epidemic that failure to implement basic source control measures with patients, visitors, and healthcare personnel with signs and symptoms of respiratory tract infection may have contributed to SARS coronavirus (SARS-CoV) transmission. This concept has been incorporated into CDC planning documents for SARS and pandemic influenza 9,10 .
- The term "Airborne Precautions" has been supplemented with the term "Airborne Infection Isolation Room (AIIR)" for consistency with the Guidelines for Environmental Infection Control in Healthcare Facilities 11 , the Guidelines for Preventing the Transmission of Mycobacterium tuberculosis in Health-Care Settings 2005 12 and the American Institute of Architects (AIA) guidelines for design and construction of hospitals, 2006 13 - A set of prevention measures termed Protective Environment has been added to the precautions used to prevent HAIs. These measures, which have been defined in other guidelines, consist of engineering and design interventions that decrease the risk of exposure to environmental fungi for severely immunocompromised allogeneic hematiopoietic stem cell transplant (HSCT) patients during their highest risk phase, usually the first 100 days post transplant, or longer in the presence of graft-versushost disease 11, . Recommendations for a Protective Environment apply only to acute care hospitals that provide care to HSCT patients.
Scope. This guideline, like its predecessors, focuses primarily on interactions between patients and healthcare providers. The Guidelines for the Prevention of MDRO Infection were published separately in November 2006, and are available online at Management of Multidrug-Resistant Organisms in Healthcare Settings (/). Several other HICPAC guidelines to prevent transmission of infectious agents associated with healthcare delivery are cited; e.g., Guideline for Hand Hygiene, Guideline for Environmental Infection Control, Guideline for Prevention of Healthcare-Associated Pneumonia, and Guideline for Infection Control in Healthcare Personnel 11,14,16,17 . In combination, these provide comprehensive guidance on the primary infection control measures for ensuring a safe environment for patients and healthcare personnel.
This guideline does not discuss in detail specialized infection control issues in defined populations that are addressed elsewhere, (e.g.  12, . An exception has been made by including abbreviated guidance for a Protective Environment used for allogeneic HSCT recipients because components of the Protective Environment have been more completely defined since publication of the Guidelines for Preventing Opportunistic Infections Among HSCT Recipients in 2000 and the Guideline for Environmental Infection Control in Healthcare Facilities 11,15 .

# I.B. Rationale for Standard and Transmission-Based Precautions in healthcare settings
Transmission of infectious agents within a healthcare setting requires three elements: a source (or reservoir) of infectious agents, a susceptible host with a portal of entry receptive to the agent, and a mode of transmission for the agent. This section describes the interrelationship of these elements in the epidemiology of HAIs.

# I.B.1. Sources of infectious agents.
Infectious agents transmitted during healthcare derive primarily from human sources but inanimate environmental sources also are implicated in transmission. Human reservoirs include patients  , healthcare personnel 29-35 17, 36-39 , and household members and other visitors  . Such source individuals may have active infections, may be in the asymptomatic and/or incubation period of an infectious disease, or may be transiently or chronically colonized with pathogenic microorganisms, particularly in the respiratory and gastrointestinal tracts. The endogenous flora of patients (e.g., bacteria residing in the respiratory or gastrointestinal tract) also are the source of HAIs  .

# I.B.2. Susceptible hosts.
Infection is the result of a complex interrelationship between a potential host and an infectious agent. Most of the factors that influence infection and the occurrence and severity of disease are related to the host. However, characteristics of the host-agent interaction as it relates to pathogenicity, virulence and antigenicity are also important, as are the infectious dose, mechanisms of disease production and route of exposure 55 . There is a spectrum of possible outcomes following exposure to an infectious agent. Some persons exposed to pathogenic microorganisms never develop symptomatic disease while others become severely ill and even die. Some individuals are prone to becoming transiently or permanently colonized but remain asymptomatic.
Still others progress from colonization to symptomatic disease either immediately following exposure, or after a period of asymptomatic colonization. The immune state at the time of exposure to an infectious agent, interaction between pathogens, and virulence factors intrinsic to the agent are important predictors of an individuals' outcome. Host factors such as extremes of age and underlying disease (e.g., diabetes 56, 57 ), human immunodeficiency virus/acquired immune deficiency syndrome  58, 59 , malignancy, and transplants 18,60,61 can increase susceptibility to infection as do a variety of medications that alter the normal flora (e.g., antimicrobial agents, gastric acid suppressants, corticosteroids, antirejection drugs, antineoplastic agents, and immunosuppressive drugs). Surgical procedures and radiation therapy impair defenses of the skin and other involved organ systems. Indwelling devices such as urinary catheters, endotracheal tubes, central venous and arterial catheters  and synthetic implants facilitate development of HAIs by allowing potential pathogens to bypass local defenses that would ordinarily impede their invasion and by providing surfaces for development of bioflms that may facilitate adherence of microorganisms and protect from antimicrobial activity 65 . Some infections associated with invasive procedures result from transmission within the healthcare facility; others arise from the patient's endogenous flora  . High-risk patient populations with noteworthy risk factors for infection are discussed further in Sections I.D, I.E., and I.F.

# I.B.3. Modes of transmission.
Several classes of pathogens can cause infection, including bacteria, viruses, fungi, parasites, and prions. The modes of transmission vary by type of organism and some infectious agents may be transmitted by more than one route: some are transmitted primarily by direct or indirect contact, (e.g., Herpes simplex virus , respiratory syncytial virus, Staphylococcus aureus), others by the droplet, (e.g., influenza virus, B. pertussis) or airborne routes (e.g., M. tuberculosis). Other infectious agents, such as bloodborne viruses (e.g., hepatitis B and C viruses  and HIV are transmitted rarely in healthcare settings, via percutaneous or mucous membrane exposure. Importantly, not all infectious agents are transmitted from person to person. These are distinguished in Appendix A. The three principal routes of transmission are summarized below.

# I.B.3.a. Contact transmission.
The most common mode of transmission, contact transmission is divided into two subgroups: direct contact and indirect contact.

# I.B.3.a.i. Direct contact transmission.
Direct transmission occurs when microorganisms are transferred from one infected person to another person without a contaminated intermediate object or person. Opportunities for direct contact transmission between patients and healthcare personnel have been summarized in the Guideline for Infection Control in Healthcare Personnel, 1998 17 and include:
- blood or other blood-containing body fluids from a patient directly enters a caregiver's body through contact with a mucous membrane 66 or breaks (i.e., cuts, abrasions) in the skin 67 .
- mites from a scabies-infested patient are transferred to the skin of a caregiver while he/she is having direct ungloved contact with the patient's skin 68,69 . - a healthcare provider develops herpetic whitlow on a finger after contact with HSV when providing oral care to a patient without using gloves or HSV is transmitted to a patient from a herpetic whitlow on an ungloved hand of a healthcare worker (HCW) 70, 71 .

# I.B.3.a.ii. Indirect contact transmission.
Indirect transmission involves the transfer of an infectious agent through a contaminated intermediate object or person. In the absence of a point-source outbreak, it is difficult to determine how indirect transmission occurs. However, extensive evidence cited in the Guideline for Hand Hygiene in Health-Care Settings suggests that the contaminated hands of healthcare personnel are important contributors to indirect contact transmission 16 . Examples of opportunities for indirect contact transmission include:
- Hands of healthcare personnel may transmit pathogens after touching an infected or colonized body site on one patient or a contaminated inanimate object, if hand hygiene is not performed before touching another patient. 72,73 . - Patient-care devices (e.g., electronic thermometers, glucose monitoring devices) may transmit pathogens if devices contaminated with blood or body fluids are shared between patients without cleaning and disinfecting between patients 74 75-77 . - Shared toys may become a vehicle for transmitting respiratory viruses (e.g., respiratory syncytial virus 24,78,79 or pathogenic bacteria (e.g., Pseudomonas aeruginosa 80 ) among pediatric patients. - Instruments that are inadequately cleaned between patients before disinfection or sterilization (e.g., endoscopes or surgical instruments)  or that have manufacturing defects that interfere with the effectiveness of reprocessing 86,87 may transmit bacterial and viral pathogens.
Clothing, uniforms, laboratory coats, or isolation gowns used as personal protective equipment (PPE), may become contaminated with potential pathogens after care of a patient colonized or infected with an infectious agent, (e.g., MRSA 88 , VRE 89 , and C. difficile 90 . Although contaminated clothing has not been implicated directly in transmission, the potential exists for soiled garments to transfer infectious agents to successive patients.

# I.B.3.b. Droplet transmission.
Droplet transmission is, technically, a form of contact transmission, and some infectious agents transmitted by the droplet route also may be transmitted by the direct and indirect contact routes. However, in contrast to contact transmission, respiratory droplets carrying infectious pathogens transmit infection when they travel directly from the respiratory tract of the infectious individual to susceptible mucosal surfaces of the recipient, generally over short distances, necessitating facial protection. Respiratory droplets are generated when an infected person coughs, sneezes, or talks 91,92 or during procedures such as suctioning, endotracheal intubation,  , cough induction by chest physiotherapy 97 and cardiopulmonary resuscitation 98,99 . Evidence for droplet transmission comes from epidemiological studies of disease outbreaks  , experimental studies 104 and from information on aerosol dynamics 91,105 . Studies have shown that the nasal mucosa, conjunctivae and less frequently the mouth, are susceptible portals of entry for respiratory viruses 106 . The maximum distance for droplet transmission is currently unresolved, although pathogens transmitted by the droplet route have not been transmitted through the air over long distances, in contrast to the airborne pathogens discussed below. Historically, the area of defined risk has been a distance of 3 feet around the patient and is based on epidemiologic and simulated studies of selected infections 103,104 . Using this distance for donning masks has been effective in preventing transmission of infectious agents via the droplet route. However, experimental studies with smallpox 107,108 and investigations during the global SARS outbreaks of 2003 101 suggest that droplets from patients with these two infections could reach persons located 6 feet or more from their source. It is likely that the distance droplets travel depends on the velocity and mechanism by which respiratory droplets are propelled from the source, the density of respiratory secretions, environmental factors such as temperature and humidity, and the ability of the pathogen to maintain infectivity over that distance 105 . Thus, a distance of 3 feet around the patient is best viewed as an example of what is meant by "a short distance from a patient" and should not be used as the sole criterion for deciding when a mask should be donned to protect from droplet exposure. Based on these considerations, it may be prudent to don a mask when within 6 to 10 feet of the patient or upon entry into the patient's room, especially when exposure to emerging or highly virulent pathogens is likely. More studies are needed to improve understanding of droplet transmission under various circumstances.
Droplet size is another variable under discussion. Droplets traditionally have been defined as being >5 m in size. Droplet nuclei, particles arising from desiccation of suspended droplets, have been associated with airborne transmission and defined as 5 m in size 105 , a reflection of the pathogenesis of pulmonary tuberculosis which is not generalizeable to other organisms. Observations of particle dynamics have demonstrated that a range of droplet sizes, including those with diameters of 30m or greater, can remain suspended in the air 109 . The behavior of droplets and droplet nuclei affect recommendations for preventing transmission. Whereas fine airborne particles containing pathogens that are able to remain infective may transmit infections over long distances, requiring AIIR to prevent its dissemination within a facility; organisms transmitted by the droplet route do not remain infective over long distances, and therefore do not require special air handling and ventilation. Examples of infectious agents that are transmitted via the droplet route include Bordetella pertussis 110 , influenza virus 23 , adenovirus 111 , rhinovirus 104 , Mycoplasma pneumoniae 112 , SARS-associated coronavirus (SARS-CoV) 21,96,113 , group A streptococcus 114 , and Neisseria meningitidis 95,103,115 . Although respiratory syncytial virus may be transmitted by the droplet route, direct contact with infected respiratory secretions is the most important determinant of transmission and consistent adherence to Standard plus Contact Precautions prevents transmission in healthcare settings 24,116,117 .
Rarely, pathogens that are not transmitted routinely by the droplet route are dispersed into the air over short distances. For example, although S. aureus is transmitted most frequently by the contact route, viral upper respiratory tract infection has been associated with increased dispersal of S. aureus from the nose into the air for a distance of 4 feet under both outbreak and experimental conditions and is known as the "cloud baby" and "cloud adult" phenomenon  .

# I.B.3.c. Airborne transmission.
Airborne transmission occurs by dissemination of either airborne droplet nuclei or small particles in the respirable size range containing infectious agents that remain infective over time and distance (e.g., spores of Aspergillus spp, and Mycobacterium tuberculosis). Microorganisms carried in this manner may be dispersed over long distances by air currents and may be inhaled by susceptible individuals who have not had face-to-face contact with (or been in the same room with) the infectious individual  . Preventing the spread of pathogens that are transmitted by the airborne route requires the use of special air handling and ventilation systems (e.g., AIIRs) to contain and then safely remove the infectious agent 11,12 .
Infectious agents to which this applies include Mycobacterium tuberculosis  , rubeola virus (measles) 122 , and varicella-zoster virus (chickenpox) 123 . In addition, published data suggest the possibility that variola virus (smallpox) may be transmitted over long distances through the air under unusual circumstances and AIIRs are recommended for this agent as well; however, droplet and contact routes are the more frequent routes of transmission for smallpox 108,128,129 . In addition to AIIRs, respiratory protection with NIOSH certified N95 or higher level respirator is recommended for healthcare personnel entering the AIIR to prevent acquisition of airborne infectious agents such as M. tuberculosis 12 .
For certain other respiratory infectious agents, such as influenza 130,131 and rhinovirus 104 , and even some gastrointestinal viruses (e.g., norovirus 132 and rotavirus 133 ) there is some evidence that the pathogen may be transmitted via small-particle aerosols, under natural and experimental conditions. Such transmission has occurred over distances longer than 3 feet but within a defined airspace (e.g., patient room), suggesting that it is unlikely that these agents remain viable on air currents that travel long distances. AIIRs are not required routinely to prevent transmission of these agents. Additional issues concerning examples of small particle aerosol transmission of agents that are most frequently transmitted by the droplet route are discussed below.

# I.B.3.d. Emerging issues concerning airborne transmission of infectious agents.

# I.B.3.d.i. Transmission from patients.
The emergence of SARS in 2002, the importation of monkeypox into the United States in 2003, and the emergence of avian influenza present challenges to the assignment of isolation categories because of conflicting information and uncertainty about possible routes of transmission. Although SARS-CoV is transmitted primarily by contact and/or droplet routes, airborne transmission over a limited distance (e.g., within a room), has been suggested, though not proven  . This is true of other infectious agents such as influenza virus 130 and noroviruses 132,142,143 . Influenza viruses are transmitted primarily by close contact with respiratory droplets 23,102 and acquisition by healthcare personnel has been prevented by Droplet Precautions, even when positive pressure rooms were used in one center 144 However, inhalational transmission could not be excluded in an outbreak of influenza in the passengers and crew of a single aircraft 130 . Observations of a protective effect of UV lights in preventing influenza among patients with tuberculosis during the influenza pandemic of 1957-'58 have been used to suggest airborne transmission 145,146 .
In contrast to the strict interpretation of an airborne route for transmission (i.e., long distances beyond the patient room environment), short distance transmission by small particle aerosols generated under specific circumstances (e.g., during endotracheal intubation) to persons in the immediate area near the patient has been demonstrated. Also, aerosolized particles <100 m can remain suspended in air when room air current velocities exceed the terminal settling velocities of the particles 109 . SARS-CoV transmission has been associated with endotracheal intubation, noninvasive positive pressure ventilation, and cardio-pulmonary resuscitation 93,94,96,98,141 . Although the most frequent routes of transmission of noroviruses are contact and food and waterborne routes, several reports suggest that noroviruses may be transmitted through aerosolization of infectious particles from vomitus or fecal material 142,143,147,148 . It is hypothesized that the aerosolized particles are inhaled and subsequently swallowed.
Roy and Milton proposed a new classification for aerosol transmission when evaluating routes of SARS transmission:
1. obligate: under natural conditions, disease occurs following transmission of the agent only through inhalation of small particle aerosols (e.g., tuberculosis); 2. preferential: natural infection results from transmission through multiple routes, but small particle aerosols are the predominant route (e.g., measles, varicella); and 3. opportunistic: agents that naturally cause disease through other routes, but under special circumstances may be transmitted via fine particle aerosols 149 .
This conceptual framework can explain rare occurrences of airborne transmission of agents that are transmitted most frequently by other routes (e.g., smallpox, SARS, influenza, noroviruses). Concerns about unknown or possible routes of transmission of agents associated with severe disease and no known treatment often result in more extreme prevention strategies than may be necessary; therefore, recommended precautions could change as the epidemiology of an emerging infection is defined and controversial issues are resolved.

# I.B.3.d.ii.
Transmission from the environment. Some airborne infectious agents are derived from the environment and do not usually involve person-to-person transmission.
For example, anthrax spores present in a finely milled powdered preparation can be aerosolized from contaminated environmental surfaces and inhaled into the respiratory tract 150,151 . Spores of environmental fungi (e.g., Aspergillus spp.) are ubiquitous in the environment and may cause disease in immunocompromised patients who inhale aerosolized (e.g., via construction dust) spores 152,153 . As a rule, neither of these organisms is subsequently transmitted from infected patients. However, there is one welldocumented report of person-to-person transmission of Aspergillus sp. in the ICU setting that was most likey due to the aerosolization of spores during wound debridement 154 . A Protective Environment refers to isolation practices designed to decrease the risk of exposure to environmental fungal agents in allogeneic HSCT patients 11,14,15, .
Environmental sources of respiratory pathogens (eg. Legionella) transmitted to humans through a common aerosol source is distinct from direct patient-to-patient transmission.

# I.B.3.e. Other sources of infection.
Transmission of infection from sources other than infectious individuals include those associated with common environmental sources or vehicles (e.g., contaminated food, water, or medications (e.g., intravenous fluids). Although Aspergillus spp. have been recovered from hospital water systems 159 , the role of water as a reservoir for immunosuppressed patients remains uncertain. Vectorborne transmission of infectious agents from mosquitoes, flies, rats, and other vermin also can occur in healthcare settings. Prevention of vector borne transmission is not addressed in this document.

# I.C. Infectious Agents of Special Infection Control Interest for Healthcare Settings
Several infectious agents with important infection control implications that either were not discussed extensively in previous isolation guidelines or have emerged recently are discussed below. These are epidemiologically important organisms (e.g., C. difficile), agents of bioterrorism, prions, SARS-CoV, monkeypox, noroviruses, and the hemorrhagic fever viruses. Experience with these agents has broadened the understanding of modes of transmission and effective preventive measures. These agents are included for purposes of information and, for some (i.e., SARS-CoV, monkeypox), because of the lessons that have been learned about preparedness planning and responding effectively to new infectious agents.

# I.C.1. Epidemiologically important organisms.
Any infectious agents transmitted in healthcare settings may, under defined conditions, become targeted for control because they are epidemiologically important. C. difficile is specifically discussed below because of wide recognition of its current importance in U.S. healthcare facilities. In determining what constitutes an "epidemiologically important organism", the following characteristics apply:
- A propensity for transmission within healthcare facilities based on published reports and the occurrence of temporal or geographic clusters of > 2 patients, (e.g., C..difficile, norovirus, respiratory syncytial virus (RSV), influenza, rotavirus, Enterobacter spp; Serratia spp., group A streptococcus). A single case of healthcare-associated invasive disease caused by certain pathogens (e.g., group A streptococcus post-operatively 160 , in burn units 161 , or in a LTCF 162 ; Legionella sp. 14, 163 , Aspergillus sp. 164 ) is generally considered a trigger for investigation and enhanced control measures because of the risk of additional cases and severity of illness associated with these infections. Antimicrobial resistance - Resistance to first-line therapies (e.g., MRSA, VISA, VRSA, VRE, ESBL-producing organisms). - Common and uncommon microorganisms with unusual patterns of resistance within a facility (e.g., the first isolate of Burkholderia cepacia complex or Ralstonia spp. in non-CF patients or a quinolone-resistant strain of Pseudomonas aeruginosa in a facility). - Difficult to treat because of innate or acquired resistance to multiple classes of antimicrobial agents (e.g., Stenotrophomonas maltophilia, Acinetobacter spp.). - Association with serious clinical disease, increased morbidity and mortality (e.g., MRSA and MSSA, group A streptococcus) - A newly discovered or reemerging pathogen I.C.1.a. C.difficile. C. difficile is a spore-forming gram positive anaerobic bacillus that was first isolated from stools of neonates in 1935 165 and identified as the most commonly identified causative agent of antibiotic-associated diarrhea and pseudomembranous colitis in 1977 166 . This pathogen is a major cause of healthcareassociated diarrhea and has been responsible for many large outbreaks in healthcare settings that were extremely difficult to control. Important factors that contribute to healthcare-associated outbreaks include environmental contamination, persistence of spores for prolonged periods of time, resistance of spores to routinely used disinfectants and antiseptics, hand carriage by healthcare personnel to other patients, and exposure of patients to frequent courses of antimicrobial agents 167 . Antimicrobials most frequently associated with increased risk of C. difficile include third generation cephalosporins, clindamycin, vancomycin, and fluoroquinolones.
Since 2001, outbreaks and sporadic cases of C. difficile with increased morbidity and mortality have been observed in several U.S. states, Canada, England and the Netherlands  . The same strain of C. difficile has been implicated in these outbreaks 173 . This strain, toxinotype III, North American PFGE type 1, and PCRribotype 027 (NAP1/027) has been found to hyperproduce toxin A (16 fold increase) and toxin B (23 fold increase) compared with isolates from 12 different pulsed-field gel electrophoresisPFGE types. A recent survey of U.S. infectious disease physicians found that 40% perceived recent increases in the incidence and severity of C. difficile disease 174 . Standardization of testing methodology and surveillance definitions is needed for accurate comparisons of trends in rates among hospitals 175 . It is hypothesized that the incidence of disease and apparent heightened transmissibility of this new strain may be due, at least in part, to the greater production of toxins A and B, increasing the severity of diarrhea and resulting in more environmental contamination. Considering the greater morbidity, mortality, length of stay, and costs associated with C. difficile disease in both acute care and long term care facilities, control of this pathogen is now even more important than previously. Prevention of transmission focuses on syndromic application of Contact Precautions for patients with diarrhea, accurate identification of patients, environmental measures (e.g., rigorous cleaning of patient rooms) and consistent hand hygiene. Use of soap and water, rather than alcohol based handrubs, for mechanical removal of spores from hands, and a bleach-containing disinfectant (5000 ppm) for environmental disinfection, may be valuable when there is transmission in a healthcare facility. See Appendix A for specific recommendations.

# I.C.1. b. Multidrug-resistant organisms (MDROs).
In general, MDROs are defined as microorganisms -predominantly bacteria -that are resistant to one or more classes of antimicrobial agents 176 . Although the names of certain MDROs suggest resistance to only one agent (e.g., methicillin-resistant Staphylococcus aureus , vancomycin resistant enterococcus ), these pathogens are usually resistant to all but a few commercially available antimicrobial agents. This latter feature defines MDROs that are considered to be epidemiologically important and deserve special attention in healthcare facilities 177 . Other MDROs of current concern include multidrug-resistant Streptococcus pneumoniae (MDRSP) which is resistant to penicillin and other broadspectrum agents such as macrolides and fluroquinolones, multidrug-resistant gramnegative bacilli (MDR-GNB), especially those producing extended spectrum betalactamases (ESBLs); and strains of S. aureus that are intermediate or resistant to vancomycin (i.e., VISA and VRSA) 178-197 198 .
MDROs are transmitted by the same routes as antimicrobial susceptible infectious agents. Patient-to-patient transmission in healthcare settings, usually via hands of HCWs, has been a major factor accounting for the increase in MDRO incidence and prevalence, especially for MRSA and VRE in acute care facilities  . Preventing the emergence and transmission of these pathogens requires a comprehensive approach that includes administrative involvement and measures (e.g., nurse staffing, communication systems, performance improvement processes to ensure adherence to recommended infection control measures), education and training of medical and other healthcare personnel, judicious antibiotic use, comprehensive surveillance for targeted MDROs, application of infection control precautions during patient care, environmental measures (e.g., cleaning and disinfection of the patient care environment and equipment, dedicated single-patientuse of non-critical equipment), and decolonization therapy when appropriate.
The prevention and control of MDROs is a national priority -one that requires that all healthcare facilities and agencies assume responsibility and participate in communitywide control programs 176,177 . A detailed discussion of this topic and recommendations for prevention was published in 2006 may be found at Management of Multidrug-Resistant Organisms in Healthcare Settings (2006) (/).

# I.C.2. Agents of bioterrorism.
CDC has designated the agents that cause anthrax, smallpox, plague, tularemia, viral hemorrhagic fevers, and botulism as Category A (high priority) because these agents can be easily disseminated environmentally and/or transmitted from person to person; can cause high mortality and have the potential for major public health impact; might cause public panic and social disruption; and require special action for public health preparedness 202 . General information relevant to infection control in healthcare settings for Category A agents of bioterrorism is summarized in Table 3. Consult  for additional, updated Category A agent information as well as information concerning Category B and C agents of bioterrorism and updates. Category B and C agents are important but are not as readily disseminated and cause less morbidity and mortality than Category A agents.
Healthcare facilities confront a different set of issues when dealing with a suspected bioterrorism event as compared with other communicable diseases. An understanding of the epidemiology, modes of transmission, and clinical course of each disease, as well as carefully drafted plans that provide an approach and relevant websites and other resources for disease-specific guidance to healthcare, administrative, and support personnel, are essential for responding to and managing a bioterrorism event. Infection control issues to be addressed include: 1. identifying persons who may be exposed or infected; 2. preventing transmission among patients, healthcare personnel, and visitors; 3. providing treatment, chemoprophylaxis or vaccine to potentially large numbers of people; 4. protecting the environment including the logistical aspects of securing sufficient numbers of AIIRs or designating areas for patient cohorts when there are an insufficient number of AIIRs available; 5. providing adequate quantities of appropriate personal protective equipment; and 6. identifying appropriate staff to care for potentially infectious patients (e.g., vaccinated healthcare personnel for care of patients with smallpox).
The response is likely to differ for exposures resulting from an intentional release compared with naturally occurring disease because of the large number persons that can be exposed at the same time and possible differences in pathogenicity.  203 ; smallpox  ; plague 207,208 ; botulinum toxin 209 ; tularemia 210 ; and hemorrhagic fever viruses: 211,212 .

# I.C.2.a. Pre-event administration of smallpox (vaccinia) vaccine to healthcare personnel.
Vaccination of personnel in preparation for a possible smallpox exposure has important infection control implications  . These include the need for meticulous screening for vaccine contraindications in persons who are at increased risk for adverse vaccinia events; containment and monitoring of the vaccination site to prevent transmission in the healthcare setting and at home; and the management of patients with vaccinia-related adverse events 216,217 . The pre-event U.S. smallpox vaccination program of 2003 is an example of the effectiveness of carefully developed recommendations for both screening potential vaccinees for contraindications and vaccination site care and monitoring. Approximately 760,000 individuals were vaccinated in the Department of Defense and 40,000 in the civilian or public health populations from December 2002 to February 2005, including approximately 70,000 who worked in healthcare settings. There were no cases of eczema vaccinatum, progressive vaccinia, fetal vaccinia, or contact transfer of vaccinia in healthcare settings or in military workplaces 218,219 . Outside the healthcare setting, there were 53 cases of contact transfer from military vaccinees to close personal contacts (e.g., bed partners or contacts during participation in sports such as wrestling 220 ). All contact transfers were from individuals who were not following recommendations to cover their vaccination sites. Vaccinia virus was confirmed by culture or PCR in 30 cases, and two of the confirmed cases resulted from tertiary transfer. All recipients, including one breast-fed infant, recovered without complication. Subsequent studies using viral culture and PCR techniques have confirmed the effectiveness of semipermeable dressings to contain vaccinia  . This experience emphasizes the importance of ensuring that newly vaccinated healthcare personnel adhere to recommended vaccination-site care, especially if they are to care for high-risk patients.
Recommendations for pre-event smallpox vaccination of healthcare personnel and vaccinia-related infection control recommendations are published in the MMWR 216,225 with updates posted on the CDC bioterrorism web site 205 .

# I.C.3. Prions.
Creutzfeldt-Jakob disease (CJD) is a rapidly progressive, degenerative, neurologic disorder of humans with an incidence in the United States of approximately 1 person/million population/year 226,227 228,229 , from implantation of contaminated human dura mater grafts 230 or from corneal transplants 231 ). Transmission has been linked to the use of contaminated neurosurgical instruments or stereotactic electroencephalogram electrodes 232,233,234,235 .
Prion diseases in animals include scrapie in sheep and goats, bovine spongiform encephalopathy (BSE, or "mad cow disease") in cattle, and chronic wasting disease in deer and elk 236 . BSE, first recognized in the United Kingdom (UK) in 1986, was associated with a major epidemic among cattle that had consumed contaminated meat and bone meal.
The possible transmission of BSE to humans causing variant CJD (vCJD) was first described in 1996 and subsequently found to be associated with consumption of BSEcontaminated cattle products primarily in the United Kingdom. There is strong epidemiologic and laboratory evidence for a causal association between the causative agent of BSE and vCJD 237 . Although most cases of vCJD have been reported from the UK, a few cases also have been reported from Europe, Japan, Canada, and the United States. Most vCJD cases worldwide lived in or visited the UK during the years of a large outbreak of BSE (1980-96) and may have consumed contaminated cattle products during that time (Creutzfeldt-Jakob Disease, Classic (CJD) () ). Although there has been no indigenously acquired vCJD in the United States, the sporadic occurrence of BSE in cattle in North America has heightened awareness of the possibility that such infections could occur and have led to increased surveillance activities. Updated information may be found on the following website: Creutzfeldt-Jakob Disease, Classic (CJD) () . The public health impact of prion diseases has been reviewed 238 .
vCJD in humans has different clinical and pathologic characteristics from sporadic or classic CJD 239 , including the following: 1. younger median age at death: 28 (range 16-48) vs. 68 years; 2. longer duration of illness: median 14 months vs. 4-6 months; 3. increased frequency of sensory symptoms and early psychiatric symptoms with delayed onset of frank neurologic signs; and 4. detection of prions in tonsillar and other lymphoid tissues from vCJD patients but not from sporadic CJD patients 240 .
Similar to sporadic CJD, there have been no reported cases of direct human-to-human transmission of vCJD by casual or environmental contact, droplet, or airborne routes.
Ongoing blood safety surveillance in the U.S. has not detected sporadic CJD transmission through blood transfusion  . However, bloodborne transmission of vCJD is believed to have occurred in two UK patients 244,245 247,248 . The incubation period from exposure to the onset of symptoms is 2 to 7 days but can be as long as 10 days and uncommonly even longer 249 . The illness is initially difficult to distinguish from other common respiratory infections. Outbreaks in healthcare settings, with transmission to large numbers of healthcare personnel and patients have been a striking feature of SARS; undiagnosed, infectious patients and visitors were important initiators of these outbreaks 21, . The relative contribution of potential modes of transmission is not precisely known. There is ample evidence for droplet and contact transmission 96,101,113 ; however, opportunistic airborne transmission cannot be excluded 101, 135-139, 149, 255 . For example, exposure to aerosolgenerating procedures (e.g., endotracheal intubation, suctioning) was associated with transmission of infection to large numbers of healthcare personnel outside of the United States 93,94,96,98,253 .Therefore, aerosolization of small infectious particles generated during these and other similar procedures could be a risk factor for transmission to others within a multi-bed room or shared airspace. A review of the infection control literature generated from the SARS outbreaks of 2003 concluded that the greatest risk of transmission is to those who have close contact, are not properly trained in use of protective infection control procedures, do not consistently use PPE; and that N95 or higher respirators may offer additional protection to those exposed to aerosol-generating procedures and high risk activities 256,257 . Organizational and individual factors that affected adherence to infection control practices for SARS also were identified 257 .
Control of SARS requires a coordinated, dynamic response by multiple disciplines in a healthcare setting 9 . Early detection of cases is accomplished by screening persons with symptoms of a respiratory infection for history of travel to areas experiencing community transmission or contact with SARS patients, followed by implementation of Respiratory Hygiene/Cough Etiquette (i.e., placing a mask over the patient's nose and mouth) and physical separation from other patients in common waiting areas.The precise combination of precautions to protect healthcare personnel has not been determined.  259 . In Hong Kong, the use of Droplet and Contact Precautions, which included use of a mask but not a respirator, was effective in protecting healthcare personnel 113 . However, in Toronto, consistent use of an N95 respirator was slightly more protective than a mask 93 . It is noteworthy that there was no transmission of SARS-CoV to public hospital workers in Vietnam despite inconsistent use of infection control measures, including use of PPE, which suggests other factors (e.g., severity of disease, frequency of high risk procedures or events, environmental features) may influence opportunities for transmission 260 .
SARS-CoV also has been transmitted in the laboratory setting through breaches in recommended laboratory practices. Research laboratories where SARS-CoV was under investigation were the source of most cases reported after the first series of outbreaks in the winter and spring of 2003 261,262 . Studies of the SARS outbreaks of 2003 and transmissions that occurred in the laboratory re-affirm the effectiveness of recommended infection control precautions and highlight the importance of consistent adherence to these measures.
Lessons from the SARS outbreaks are useful for planning to respond to future public health crises, such as pandemic influenza and bioterrorism events. Surveillance for cases among patients and healthcare personnel, ensuring availability of adequate supplies and staffing, and limiting access to healthcare facilities were important factors in the response to SARS that have been summarized 9 .  263 . This outbreak demonstrates the importance of recognition and prompt reporting of unusual disease presentations by clinicians to enable prompt identification of the etiology; and the potential of epizootic diseases to spread from animal reservoirs to humans through personal and occupational exposure 264 .
Limited data on transmission of monkeypox are available. Transmission from infected animals and humans is believed to occur primarily through direct contact with lesions and respiratory secretions; airborne transmission from animals to humans is unlikely but cannot be excluded, and may have occurred in veterinary practices (e.g., during administration of nebulized medications to ill prairie dogs 265 ). Among humans, four instances of monkeypox transmission within hospitals have been reported in Africa among children, usually related to sharing the same ward or bed 266,267 . Additional recent literature documents transmission of Congo Basin monkeypox in a hospital compound for an extended number of generations 268 .
There has been no evidence of airborne or any other person-to-person transmission of monkeypox in the United States, and no new cases of monkeypox have been identified since the outbreak in June 2003 269 . The outbreak strain is a clade of monkeypox distinct from the Congo Basin clade and may have different epidemiologic properties (including human-to-human transmission potential) from monkeypox strains of the Congo Basin 270 ; this awaits further study. Smallpox vaccine is 85% protective against Congo Basin monkeypox 271 . Since there is an associated case fatality rate of 10%, administration of smallpox vaccine within 4 days to individuals who have had direct exposure to patients or animals with monkeypox is a reasonable consideration 272 . For the most current information, see CDC Monkeypox () .
I.C.6. Noroviruses. Noroviruses, formerly referred to as Norwalk-like viruses, are members of the Caliciviridae family. These agents are transmitted via contaminated food or water and from person-to-person, causing explosive outbreaks of gastrointestinal disease 273 . Environmental contamination also has been documented as a contributing factor in ongoing transmission during outbreaks 274,275 . Although noroviruses cannot be propagated in cell culture, DNA detection by molecular diagnostic techniques has facilitated a greater appreciation of their role in outbreaks of gastrointestinal disease 276 .
Reported outbreaks in hospitals 132,142,277 , nursing homes 275, , cruise ships 284,285 , hotels 143,147 , schools 148 , and large crowded shelters established for hurricane evacuees 286 , demonstrate their highly contagious nature, the disruptive impact they have in healthcare facilities and the community, and the difficulty of controlling outbreaks in settings where people share common facilites and space. Of note, there is nearly a 5 fold increase in the risk to patients in outbreaks where a patient is the index case compared with exposure of patients during outbreaks where a staff member is the index case 287 .
The average incubation period for gastroenteritis caused by noroviruses is 12-48 hours and the clinical course lasts 12-60 hours 273 . Illness is characterized by acute onset of nausea, vomiting, abdominal cramps, and/or diarrhea. The disease is largely self-limited; rarely, death caused by severe dehydration can occur, particularly among the elderly with debilitating health conditions.
The epidemiology of norovirus outbreaks shows that even though primary cases may result from exposure to a fecally-contaminated food or water, secondary and tertiary cases often result from person-to-person transmission that is facilitated by contamination of fomites 273,288 and dissemination of infectious particles, especially during the process of vomiting 132,142,143,147,148,273,279,280 . Widespread, persistent and inapparent contamination of the environment and fomites can make outbreaks extremely difficult to control 147,275,284 .These clinical observations and the detection of norovirus DNA on horizontal surfaces 5 feet above the level that might be touched normally suggest that, under certain circumstances, aerosolized particles may travel distances beyond 3 feet 147 . It is hypothesized that infectious particles may be aerosolized from vomitus, inhaled, and swallowed. In addition, individuals who are responsible for cleaning the environment may be at increased risk of infection. Development of disease and transmission may be facilitated by the low infectious dose (i.e., <100 viral particles) 289 and the resistance of these viruses to the usual cleaning and disinfection agents (i.e., may survive 10 ppm chlorine)  . An alternate phenolic agent that was shown to be effective against feline calicivirus was used for environmental cleaning in one outbreak 275,293 . There are insufficient data to determine the efficacy of alcohol-based hand rubs against noroviruses when the hands are not visibly soiled 294 . Absence of disease in certain individuals during an outbreak may be explained by protection from infection conferred by the B histo-blood group antigen 295 . Consultation on outbreaks of gastroenteritis is available through CDC's Division of Viral and Rickettsial Diseases 296 .

# I.C.7. Hemorrhagic fever viruses (HFV).
The hemorrhagic fever viruses are a mixed group of viruses that cause serious disease with high fever, skin rash, bleeding diathesis, and in some cases, high mortality; the disease caused is referred to as viral hemorrhagic fever (VHF). Among the more commonly known HFVs are Ebola and Marburg viruses (Filoviridae), Lassa virus (Arenaviridae), Crimean-Congo hemorrhagic fever and Rift Valley Fever virus (Bunyaviridae), and Dengue and Yellow fever viruses (Flaviviridae) 212,297 . These viruses are transmitted to humans via contact with infected animals or via arthropod vectors. While none of these viruses is endemic in the United States, outbreaks in affected countries provide potential opportunities for importation by infected humans and animals. Furthermore, there are concerns that some of these agents could be used as bioweapons 212 . Person-to-person transmission is documented for Ebola, Marburg, Lassa and Crimean-Congo hemorrhagic fever viruses. In resource-limited healthcare settings, transmission of these agents to healthcare personnel, patients and visitors has been described and in some outbreaks has accounted for a large proportion of cases  . Transmissions within households also have occurred among individuals who had direct contact with ill persons or their body fluids, but not to those who did not have such contact 301 .
Evidence concerning the transmission of HFVs has been summarized 212,302 . Person-toperson transmission is associated primarily with direct blood and body fluid contact. Percutaneous exposure to contaminated blood carries a particularly high risk for transmission and increased mortality 303,304 . The finding of large numbers of Ebola viral particles in the skin and the lumina of sweat glands has raised concern that transmission could occur from direct contact with intact skin though epidemiologic evidence to support this is lacking 305 . Postmortem handling of infected bodies is an important risk for transmission 301,306,307 . In rare situations, cases in which the mode of transmission was unexplained among individuals with no known direct contact, have led to speculation that airborne transmission could have occurred 298 . However, airborne transmission of naturally occurring HFVs in humans has not been seen. In one study of airplane passengers exposed to an in-flight index case of Lassa fever, there was no transmission to any passengers 308 .
In the laboratory setting, animals have been infected experimentally with Marburg or Ebola viruses via direct inoculation of the nose, mouth and/or conjunctiva 309,310 and by using mechanically generated virus-containing aerosols 311,312 . Transmission of Ebola virus among laboratory primates in an animal facility has been described 313 . Secondarily infected animals were in individual cages and separated by approximately 3 meters. Although the possibility of airborne transmission was suggested, the authors were not able to exclude droplet or indirect contact transmission in this incidental observation.
Guidance on infection control precautions for HVFs that are transmitted person-to-person have been published by CDC 1, 211 and by the Johns Hopkins Center for Civilian Biodefense Strategies 212 . The most recent recommendations at the time of publication of this document were posted on the CDC website on 5/19/05 314 . Inconsistencies among the various recommendations have raised questions about the appropriate precautions to use in U.S. hospitals. In less developed countries, outbreaks of HFVs have been controlled with basic hygiene, barrier precautions, safe injection practices, and safe burial practices 299,306 . The preponderance of evidence on HFV transmission indicates that Standard, Contact and Droplet Precautions with eye protection are effective in protecting healthcare personnel and visitors who may attend an infected patient. Single gloves are adequate for routine patient care; double-gloving is advised during invasive procedures (e.g., surgery) that pose an increased risk for blood exposure. Routine eye protection (i.e. goggles or face shield) is particularly important. Fluid-resistant gowns should be worn for all patient contact. Airborne Precautions are not required for routine patient care; however, use of AIIRs is prudent when procedures that could generate infectious aerosols are performed (e.g., endotracheal intubation, bronchoscopy, suctioning, autopsy procedures involving oscillating saws). N95 or higher level respirators may provide added protection for individuals in a room during aerosol-generating procedures (Table 3, Appendix A). When a patient with a syndrome consistent with hemorrhagic fever also has a history of travel to an endemic area, precautions are initiated upon presentation and then modified as more information is obtained (Table 2). Patients with hemorrhagic fever syndrome in the setting of a suspected bioweapon attack should be managed using Airborne Precautions, including AIIRs, since the epidemiology of a potentially weaponized hemorrhagic fever virus is unpredictable.

# I.D. Transmission Risks Associated with Specific Types of Healthcare Settings
Numerous factors influence differences in transmission risks among the various healthcare settings. These include the population characteristics (e.g., increased susceptibility to infections, type and prevalence of indwelling devices), intensity of care, exposure to environmental sources, length of stay, and frequency of interaction between patients/residents with each other and with HCWs. These factors, as well as organizational priorities, goals, and resources, influence how different healthcare settings adapt transmission prevention guidelines to meet their specific needs 315,316 . Infection control management decisions are informed by data regarding institutional experience/epidemiology, trends in community and institutional HAIs, local, regional, and national epidemiology, and emerging infectious disease threats.

# I.D.1. Hospitals.
Infection transmission risks are present in all hospital settings. However, certain hospital settings and patient populations have unique conditions that predispose patients to infection and merit special mention. These are often sentinel sites for the emergence of new transmission risks that may be unique to that setting or present opportunities for transmission to other settings in the hospital.  318,319 , because of underlying diseases and conditions, the invasive medical devices and technology used in their care (e.g., central venous catheters and other intravascular devices, mechanical ventilators, extracorporeal membrane oxygenation (ECMO), hemodialysis/-filtration, pacemakers, implantable left ventricular assist devices), the frequency of contact with healthcare personnel, prolonged length of stay, and prolonged exposure to antimicrobial agents  . Furthermore, adverse patient outcomes in this setting are more severe and are associated with a higher mortality 332 . Outbreaks associated with a variety of bacterial, fungal and viral pathogens due to common-source and person-to-person transmissions are frequent in adult and pediatric ICUs 31, 333-336, 337, 338 .

# I.D.1.b. Burn units.
Burn wounds can provide optimal conditions for colonization, infection, and transmission of pathogens; infection acquired by burn patients is a frequent cause of morbidity and mortality 320,339,340 . In patients with a burn injury involving 30% of the total body surface area (TBSA), the risk of invasive burn wound infection is particularly high 341,342 . Infections that occur in patients with burn injury involving <30% TBSA are usually associated with the use of invasive devices. Methicillin-susceptible Staphylococcus aureus, MRSA, enterococci, including VRE, gram-negative bacteria, and candida are prevalent pathogens in burn infections 53,340, and outbreaks of these organisms have been reported  . Shifts over time in the predominance of pathogens causing infections among burn patients often lead to changes in burn care practices 343, . Burn wound infections caused by Aspergillus sp. or other environmental molds may result from exposure to supplies contaminated during construction 359 or to dust generated during construction or other environmental disruption 360 .
Hydrotherapy equipment is an important environmental reservoir of gram-negative organisms. Its use for burn care is discouraged based on demonstrated associations between use of contaminated hydrotherapy equipment and infections. Burn wound infections and colonization, as well as bloodstream infections, caused by multidrugresistant P. aeruginosa 361 , A. baumannii 362 , and MRSA 352 have been associated with hydrotherapy; excision of burn wounds in operating rooms is preferred.
Advances in burn care, specifically early excision and grafting of the burn wound, use of topical antimicrobial agents, and institution of early enteral feeding, have led to decreased infectious complications. Other advances have included prophylactic antimicrobial usage, selective digestive decontamination (SDD), and use of antimicrobial-coated catheters (ACC), but few epidemiologic studies and no efficacy studies have been performed to show the relative benefit of these measures 357 .
There is no consensus on the most effective infection control practices to prevent transmission of infections to and from patients with serious burns (e.g., single-bed rooms 358 , laminar flow 363 and high efficiency particulate air filtration  360 or maintaining burn patients in a separate unit without exposure to patients or equipment from other units 364 ). There also is controversy regarding the need for and type of barrier precautions for routine care of burn patients. One retrospective study demonstrated efficacy and cost effectiveness of a simplified barrier isolation protocol for wound colonization, emphasizing handwashing and use of gloves, caps, masks and plastic impermeable aprons (rather than isolation gowns) for direct patient contact 365 . However, there have been no studies that define the most effective combination of infection control precautions for use in burn settings. Prospective studies in this area are needed.

# I.D.1.c. Pediatrics.
Studies of the epidemiology of HAIs in children have identified unique infection control issues in this population 63,64, . Pediatric intensive care unit (PICU) patients and the lowest birthweight babies in the high-risk nursery (HRN) monitored in the NNIS system have had high rates of central venous catheter-associated bloodstream infections 64,320, . Additionally, there is a high prevalence of community-acquired infections among hospitalized infants and young children who have not yet become immune either by vaccination or by natural infection. The result is more patients and their sibling visitors with transmissible infections present in pediatric healthcare settings, especially during seasonal epidemics (e.g., pertussis 36,40,41 , respiratory viral infections including those caused by RSV 24 , influenza viruses 373 , parainfluenza virus 374 , human metapneumovirus 375 , and adenoviruses 376 ; rubeola  34 , varicella  377 , and rotavirus 38,378 ).
Close physical contact between healthcare personnel and infants and young children (eg. cuddling, feeding, playing, changing soiled diapers, and cleaning copious uncontrolled respiratory secretions) provides abundant opportunities for transmission of infectious material. Practices and behaviors such as congregation of children in play areas where toys and bodily secretions are easily shared and family members roomingin with pediatric patients can further increase the risk of transmission. Pathogenic bacteria have been recovered from toys used by hospitalized patients 379 ; contaminated bath toys were implicated in an outbreak of multidrug-resistant P. aeruginosa on a pediatric oncology unit 80 . In addition, several patient factors increase the likelihood that infection will result from exposure to pathogens in healthcare settings (e.g., immaturity of the neonatal immune system, lack of previous natural infection and resulting immunity, prevalence of patients with congenital or acquired immune deficiencies, congenital anatomic anomalies, and use of life-saving invasive devices in neontal and pediatric intensive care units) 63 . There are theoretical concerns that infection risk will increase in association with innovative practices used in the NICU for the purpose of improving developmental outcomes, Such factors include co-bedding 380 and kangaroo care 381 that may increase opportunity for skin-to-skin exposure of multiple gestation infants to each other and to their mothers, respectively; although infection risk smay actually be reduced among infants receiving kangaroo care 382 . Children who attend child care centers 383,384 and pediatric rehabilitation units 385 may increase the overall burden of antimicrobial resistance (eg. by contributing to the reservoir of community-associated MRSA )  . Patients in chronic care facilities may have increased rates of colonization with resistant GNBs and may be sources of introduction of resistant organisms to acute care settings 50 .

# I.D.2. Non-acute healthcare settings.
Healthcare is provided in various settings outside of hospitals including facilities, such as long-term care facilities (LTCF) (e.g., nursing homes), homes for the developmentally disabled, settings where behavioral health services are provided, rehabilitation centers and hospices 392 . In addition, healthcare may be provided in nonhealthcare settings such as workplaces with occupational health clinics, adult day care centers, assisted living facilities, homeless shelters, jails and prisons, school clinics and infirmaries. Each of these settings has unique circumstances and population risks to consider when designing and implementing an infection control program. Several of the most common settings and their particular challenges are discussed below. While this Guideline does not address each setting, the principles and strategies provided may be adapted and applied as appropriate.

# I.D.2.a. Long-term care.
The designation LTCF applies to a diverse group of residential settings, ranging from institutions for the developmentally disabled to nursing homes for the elderly and pediatric chronic-care facilities  . Nursing homes for the elderly predominate numerically and frequently represent long-term care as a group of facilities. Approximately 1.8 million Americans reside in the nation's 16,500 nursing homes. 396 Estimates of HAI rates of 1.8 to 13.5 per 1000 resident-care days have been reported with a range of 3 to 7 per 1000 resident-care days in the more rigorous studies  .
The infrastructure described in the Department of Veterans Affairs nursing home care units is a promising example for the development of a nationwide HAI surveillance system for LTCFs 402 .
LCTFs are different from other healthcare settings in that elderly patients at increased risk for infection are brought together in one setting and remain in the facility for extended periods of time; for most residents, it is their home. An atmosphere of community is fostered and residents share common eating and living areas, and participate in various facility-sponsored activities 403,404 . Since able residents interact freely with each other, controlling transmission of infection in this setting is challenging 405 . Residents who are colonized or infected with certain microorganisms are, in some cases, restricted to their room. However, because of the psychosocial risks associated with such restriction, it has been recommended that psychosocial needs be balanced with infection control needs in the LTCF setting  . Documented LTCF outbreaks have been caused by various viruses (e.g., influenza virus 35, , rhinovirus 413 , adenovirus  414 , norovirus 278, 279 275, 281 ) and bacteria (e.g., group A streptococcus 162 , B. pertussis 415 , non-susceptible S. pneumoniae 197,198 , other MDROs, and Clostridium difficile 416 ) These pathogens can lead to substantial morbidity and mortality, and increased medical costs; prompt detection and implementation of effective control measures are required.
Risk factors for infection are prevalent among LTCF residents 395,417,418 . Age-related declines in immunity may affect responses to immunizations for influenza and other infectious agents, and increase susceptibility to tuberculosis. Immobility, incontinence, dysphagia, underlying chronic diseases, poor functional status, and age-related skin changes increase susceptibility to urinary, respiratory and cutaneous and soft tissue infections, while malnutrition can impair wound healing  . Medications (e.g., drugs that affect level of consciousness, immune function, gastric acid secretions, and normal flora, including antimicrobial therapy) and invasive devices (e.g., urinary catheters and feeding tubes) heighten susceptibility to infection and colonization in LTCF residents  . Finally, limited functional status and total dependence on healthcare personnel for activities of daily living have been identified as independent risk factors for infection 401,417,427 and for colonization with MRSA 428,429 and ESBL-producing K. pneumoniae 430 .
Several position papers and review articles have been published that provide guidance on various aspects of infection control and antimicrobial resistance in LTCFs  . The Centers for Medicare and Medicaid Services (CMS) have established regulations for the prevention of infection in LTCFs 437 .
Because residents of LTCFs are hospitalized frequently, they can transfer pathogens between LTCFs and healthcare facilities in which they receive care 8, . This is also true for pediatric long-term care populations. Pediatric chronic care facilities have been associated with importing extended-spectrum cephalosporin-resistant, gram-negative bacilli into one PICU 50 . Children from pediatric rehabilitation units may contribute to the reservoir of community-associated MRSA 385, .

# I.D.2.b. Ambulatory care.
In the past decade, healthcare delivery in the United States has shifted from the acute, inpatient hospital to a variety of ambulatory and communitybased settings, including the home. Ambulatory care is provided in hospital-based outpatient clinics, nonhospital-based clinics and physician offices, public health clinics, free-standing dialysis centers, ambulatory surgical centers, urgent care centers, and many others. In 2000, there were 83 million visits to hospital outpatient clinics and more than 823 million visits to physician offices 442 ; ambulatory care now accounts for most patient encounters with the health care system 443 . In these settings, adapting transmission prevention guidelines is challenging because patients remain in common areas for prolonged periods waiting to be seen by a healthcare provider or awaiting admission to the hospital, examination or treatment rooms are turned around quickly with limited cleaning, and infectious patients may not be recognized immediately. Furthermore, immunocompromised patients often receive chemotherapy in infusion rooms where they stay for extended periods of time along with other types of patients.
There are few data on the risk of HAIs in ambulatory care settings, with the exception of hemodialysis centers 18,444,445 . Transmission of infections in outpatient settings has been reviewed in three publications  . Goodman and Solomon summarized 53 clusters of infections associated with the outpatient setting from 1961-1990 446 . Overall, 29 clusters were associated with common source transmission from contaminated solutions or equipment, 14 with person-to-person transmission from or involving healthcare personnel and ten associated with airborne or droplet transmission among patients and healthcare workers. Transmission of bloodborne pathogens (i.e., hepatitis B and C viruses and, rarely, HIV) in outbreaks, sometimes involving hundreds of patients, continues to occur in ambulatory settings. These outbreaks often are related to common source exposures, usually a contaminated medical device, multi-dose vial, or intravenous solution 82, . In all cases, transmission has been attributed to failure to adhere to fundamental infection control principles, including safe injection practices and aseptic technique.This subject has been reviewed and recommended infection control and safe injection practices summarized 454 .
Airborne transmission of M.tuberculosis and measles in ambulatory settings, most frequently emergency departments, has been reported 34,127,446,448, . Measles virus was transmitted in physician offices and other outpatient settings during an era when immunization rates were low and measles outbreaks in the community were occurring regularly 34,122,458 . Rubella has been transmitted in the outpatient obstetric setting 33 ; there are no published reports of varicella transmission in the outpatient setting. In the ophthalmology setting, adenovirus type 8 epidemic keratoconjunctivitis has been transmitted via incompletely disinfected ophthalmology equipment and/or from healthcare workers to patients, presumably by contaminated hands 17,446,448, .
If transmission in outpatient settings is to be prevented, screening for potentially infectious symptomatic and asymptomatic individuals, especially those who may be at risk for transmitting airborne infectious agents (e.g., M. tuberculosis, varicella-zoster virus, rubeola ), is necessary at the start of the initial patient encounter. Upon identification of a potentially infectious patient, implementation of prevention measures, including prompt separation of potentially infectious patients and implementation of appropriate control measures (e.g., Respiratory Hygiene/Cough Etiquette and Transmission-Based Precautions) can decrease transmission risks 9,12 . Transmission of MRSA and VRE in outpatient settings has not been reported, but the association of CA-MRSA in healthcare personnel working in an outpatient HIV clinic with environmental CA-MRSA contamination in that clinic, suggests the possibility of transmission in that setting 463 . Patient-to-patient transmission of Burkholderia species and Pseudomonas aeruginosa in outpatient clinics for adults and children with cystic fibrosis has been confirmed 464,465 .

# I.D.2.c. Home care. Home care in the United
States is delivered by over 20,000 provider agencies that include home health agencies, hospices, durable medical equipment providers, home infusion therapy services, and personal care and support services providers. Home care is provided to patients of all ages with both acute and chronic conditions. The scope of services ranges from assistance with activities of daily living and physical and occupational therapy to the care of wounds, infusion therapy, and chronic ambulatory peritoneal dialysis (CAPD).
The incidence of infection in home care patients, other than those associated with infusion therapy is not well studied  . However, data collection and calculation of infection rates have been accomplished for central venous catheter-associated bloodstream infections in patients receiving home infusion therapy  and for the risk of blood contact through percutaneous or mucosal exposures, demonstrating that surveillance can be performed in this setting 4 75 . Draft definitions for home care associated infections have been developed 476 .
Transmission risks during home care are presumed to be minimal. The main transmission risks to home care patients are from an infectious healthcare provider or contaminated equipment; providers also can be exposed to an infectious patient during home visits. Since home care involves patient care by a limited number of personnel in settings without multiple patients or shared equipment, the potential reservoir of pathogens is reduced. Infections of home care providers, that could pose a risk to home care patients include infections transmitted by the airborne or droplet routes (e.g., chickenpox, tuberculosis, influenza), and skin infestations (e.g., scabies 69 and lice) and infections (e.g.,impetigo) transmitted by direct or indirect contact. There are no published data on indirect transmission of MDROs from one home care patient to another, although this is theoretically possible if contaminated equipment is transported from an infected or colonized patient and used on another patient. Of note, investigation of the first case of VISA in homecare 186 and the first 2 reported cases of VRSA 178,180,181,183 found no evidence of transmission of VISA or VRSA to other home care recipients. Home health care also may contribute to antimicrobial resistance; a review of outpatient vancomycin use found 39% of recipients did not receive the antibiotic according to recommended guidelines 477 .
Although most home care agencies implement policies and procedures to prevent transmission of organisms, the current approach is based on the adaptation of the 1996 Guideline for Isolation Precautions in Hospitals 1 as well as other professional guidance 478, 479 . This issue has been very challenging in the home care industry and practice has been inconsistent and frequently not evidence-based. For example, many home health agencies continue to observe "nursing bag technique," a practice that prescribes the use of barriers between the nursing bag and environmental surfaces in the home 480. While the home environment may not always appear clean, the use of barriers between two non-critical surfaces has been questioned 481,482 . Opportunites exist to conduct research in home care related to infection transmission risks 483 .

# I.D.2.d. Other sites of healthcare delivery.
Facilities that are not primarily healthcare settings but in which healthcare is delivered include clinics in correctional facilities and shelters. Both settings can have suboptimal features, such as crowded conditions and poor ventilation. Economically disadvantaged individuals who may have chronic illnesses and healthcare problems related to alcoholism, injection drug use, poor nutrition, and/or inadequate shelter often receive their primary healthcare at sites such as these 484 . Infectious diseases of special concern for transmission include tuberculosis, scabies, respiratory infections (e.g., N. meningitides, S. pneumoniae), sexually transmitted and bloodborne diseases (e.g.,HIV, HBV, HCV, syphilis, gonorrhea), hepatitis A virus (HAV), diarrheal agents such as norovirus, and foodborne diseases 286, . A high index of suspicion for tuberculosis and CA-MRSA in these populations is needed as outbreaks in these settings or among the populations they serve have been reported  .
Patient encounters in these types of facilities provide an opportunity to deliver recommended immunizations and screen for M. tuberculosis infection in addition to diagnosing and treating acute illnesses 498 . Recommended infection control measures in these non-traditional areas designated for healthcare delivery are the same as for other ambulatory care settings. Therefore, these settings must be equipped to observe Standard Precautions and, when indicated, Transmission-based Precautions.

# I.E. Transmission Risks Associated with Special Patient Populations
As new treatments emerge for complex diseases, unique infection control challenges associated with special patient populations need to be addressed.

# I.E.1. Immunocompromised patients.
Patients who have congenital primary immune deficiencies or acquired disease (eg. treatment-induced immune deficiencies) are at increased risk for numerous types of infections while receiving healthcare and may be located throughout the healthcare facility. The specific defects of the immune system determine the types of infections that are most likely to be acquired (e.g., viral infections are associated with T-cell defects and fungal and bacterial infections occur in patients who are neutropenic). As a general group, immunocompromised patients can be cared for in the same environment as other patients; however, it is always advisable to minimize exposure to other patients with transmissible infections such as influenza and other respiratory viruses 499,500 . The use of more intense chemotherapy regimens for treatment of childhood leukemia may be associated with prolonged periods of neutropenia and suppression of other components of the immune system, extending the period of infection risk and raising the concern that additional precautions may be indicated for select groups 501,502 . With the application of newer and more intense immunosuppressive therapies for a variety of medical conditions (e.g., rheumatologic disease 503,504 , inflammatory bowel disease 505 ), immunosuppressed patients are likely to be more widely distributed throughout a healthcare facility rather than localized to single patient units (e.g., hematology-oncology). Guidelines for preventing infections in certain groups of immunocompromised patients have been published 15,506,507 .
Published data provide evidence to support placing allogeneic HSCT patients in a Protective Environment 15,157,158 . Also, three guidelines have been developed that address the special requirements of these immunocompromised patients, including use of antimicrobial prophylaxis and engineering controls to create a Protective Environment for the prevention of infections caused by Aspergillus spp. and other environmental fungi 11,14,15 . As more intense chemotherapy regimens associated with prolonged periods of neutropenia or graft-versus-host disease are implemented, the period of risk and duration of environmental protection may need to be prolonged beyond the traditional 100 days 508 .

# I.E.2. Cystic fibrosis patients.
Patients with cystic fibrosis (CF) require special consideration when developing infection control guidelines. Compared to other patients, CF patients require additional protection to prevent transmission from contaminated respiratory therapy equipment  . Infectious agents such as Burkholderia cepacia complex and P. aeruginosa 464,465,514,515 have unique clinical and prognostic significance. In CF patients, B. cepacia infection has been associated with increased morbidity and mortality  , while delayed acquisition of chronic P.aeruginosa infection may be associated with an improved long-term clinical outcome 519,520 .
Person-to-person transmission of B. cepacia complex has been demonstrated among children 517 and adults 521 with CF in healthcare settings 464,522 , during various social contacts 523 , most notably attendance at camps for patients with CF 524 , and among siblings with CF 525 . Successful infection control measures used to prevent transmission of respiratory secretions include segregation of CF patients from each other in ambulatory and hospital settings (including use of private rooms with separate showers), environmental decontamination of surfaces and equipment contaminated with respiratory secretions, elimination of group chest physiotherapy sessions, and disbanding of CF camps 97,526 . The Cystic Fibrosis Foundation published a consensus document with evidence-based recommendations for infection control practices for CF patients 20 .

# I.F. New Therapies Associated with Potentially Transmissible Infectious Agents

# I.F.1. Gene therapy.
Gene therapy has has been attempted using a number of different viral vectors, including nonreplicating retroviruses, adenoviruses, adeno-associated viruses, and replication-competent strains of poxviruses. Unexpected adverse events have restricted the prevalence of gene therapy protocols.
The infectious hazards of gene therapy are theoretical at this time, but require meticulous surveillance due to the possible occurrence of in vivo recombination and the subsequent emergence of a transmissible genetically altered pathogen. Greatest concern attends the use of replication-competent viruses, especially vaccinia. As of the time of publication, no reports have described transmission of a vector virus from a gene therapy recipient to another individual, but surveillance is ongoing.
Recommendations for monitoring infection control issues throughout the course of gene therapy trials have been published  .

# I.F.2. Infections transmitted through blood, organs and other tissues.
The potential hazard of transmitting infectious pathogens through biologic products is a small but ever present risk, despite donor screening. Reported infections transmitted by transfusion or transplantation include West Nile Virus infection 530 cytomegalovirus infection 531 , Creutzfeldt-Jacob disease 230 , hepatitis C 532 , infections with Clostridium spp. 533 and group A streptococcus 534 , malaria 535 , babesiosis 536 , Chagas disease 537 , lymphocytic choriomeningitis 538 , and rabies 539,540 . Therefore, it is important to consider receipt of biologic products when evaluating patients for potential sources of infection.

# I.F.3. Xenotransplantation.
The transplantation of nonhuman cells, tissues, and organs into humans potentially exposes patients to zoonotic pathogens. Transmission of known zoonotic infections (e.g., trichinosis from porcine tissue), constitutes one concern, but also of concern is the possibility that transplantation of nonhuman cells, tissues, or organs may transmit previously unknown zoonotic infections (xenozoonoses) to immunosuppressed human recipients. Potential infections that might accompany transplantation of porcine organs have been described 541 . Guidelines from the U.S. Public Health Service address many infectious diseases and infection control issues that surround the developing field of xenotransplantation, 542 work in this area is ongoing.

# Part II: Fundamental Elements Needed to Prevent Transmission of Infectious Agents in Healthcare Settings

# II.A. Healthcare System Components that Influence the Effectiveness of Precautions to Prevent Transmission

# II.A.1. Administrative measures.
Healthcare organizations can demonstrate a commitment to preventing transmission of infectious agents by incorporating infection control into the objectives of the organization's patient and occupational safety programs  . An infrastructure to guide, support, and monitor adherence to Standard and Transmission-Based Precautions 434,548,549 will facilitate fulfillment of the organization's mission and achievement of the Joint Commission on Accreditation of Healthcare Organization's patient safety goal to decrease HAIs 550 . Policies and procedures that explain how Standard and Transmission-Based Precautions are applied, including systems used to identify and communicate information about patients with potentially transmissible infectious agents, are essential to ensure the success of these measures and may vary according to the characteristics of the organization.
A key administrative measure is provision of fiscal and human resources for maintaining infection control and occupational health programs that are responsive to emerging needs. Specific components include bedside nurse 551 and infection prevention and control professional (ICP) staffing levels 552 , inclusion of ICPs in facility construction and design decisions 11 , clinical microbiology laboratory support 553,554 , adequate supplies and equipment including facility ventilation systems 11 , adherence monitoring 555 , assessment and correction of system failures that contribute to transmission 556,557 , and provision of feedback to healthcare personnel and senior administrators 434,548,549,558 . The positive influence of institutional leadership has been demonstrated repeatedly in studies of HCW adherence to recommended hand hygiene practices 176,177,434,548,549, . Healthcare administrator involvement in infection control processes can improve administrators' awareness of the rationale and resource requirements for following recommended infection control practices.
Several administrative factors may affect the transmission of infectious agents in healthcare settings: institutional culture, individual worker behavior, and the work environment. Each of these areas is suitable for performance improvement monitoring and incorporation into the organization's patient safety goals 543,544,546,565 .

# II.A.1.a.Scope of work and staffing needs for infection control professionals.
The effectiveness of infection surveillance and control programs in preventing nosocomial infections in United States hospitals was assessed by the CDC through the Study on the Efficacy of Nosocomial Infection Control (SENIC Project) conducted 1970-76 566 . In a representative sample of US general hospitals, those with a trained infection control physician or microbiologist involved in an infection control program, and at least one infection control nurse per 250 beds, were associated with a 32% lower rate of four infections studied (CVC-associated bloodstream infections, ventilator-associated pneumonias, catheter-related urinary tract infections, and surgical site infections).
Since that landmark study was published, responsibilities of ICPs have expanded commensurate with the growing complexity of the healthcare system, the patient populations served, and the increasing numbers of medical procedures and devices used in all types of healthcare settings. The scope of work of ICPs was first assessed in 1982  by the Certification Board of Infection Control (CBIC), and has been reassessed every five years since that time 558, . The findings of these task analyses have been used to develop and update the Infection Control Certification Examination, offered for the first time in 1983. With each survey, it is apparent that the role of the ICP is growing in complexity and scope, beyond traditional infection control activities in acute care hospitals. Activities currently assigned to ICPs in response to emerging challenges include: 1. surveillance and infection prevention at facilities other than acute care hospitals e.g., ambulatory clinics, day surgery centers, long term care facilities, rehabilitation centers, home care; 2. oversight of employee health services related to infection prevention, e.g., assessment of risk and administration of recommended treatment following exposure to infectious agents, tuberculosis screening, influenza vaccination, respiratory protection fit testing, and administration of other vaccines as indicated, such as smallpox vaccine in 2003; 3. preparedness planning for annual influenza outbreaks, pandemic influenza, SARS, bioweapons attacks; 4. adherence monitoring for selected infection control practices; 5. oversight of risk assessment and implementation of prevention measures associated with construction and renovation; 6. prevention of transmission of MDROs; 7. evaluation of new medical products that could be associated with increased infection risk. e.g.,intravenous infusion materials; 8. communication with the public, facility staff, and state and local health departments concerning infection control-related issues; and 9. participation in local and multi-center research projects 434,549,552,558,573,574 .
None of the CBIC job analyses addressed specific staffing requirements for the identified tasks, although the surveys did include information about hours worked; the 2001 survey included the number of ICPs assigned to the responding facilities 558 . There is agreement in the literature that 1 ICP per 250 acute care beds is no longer adequate to meet current infection control needs; a Delphi project that assessed staffing needs of infection control programs in the 21st century concluded that a ratio of 0.8 to 1.0 ICP per 100 occupied acute care beds is an appropriate level of staffing 552 . A survey of participants in the National Nosocomial Infections Surveillance (NNIS) system found the average daily census per ICP was 115 316 . Results of other studies have been similar: 3 per 500 beds for large acute care hospitals, 1 per 150-250 beds in long term care facilities, and 1.56 per 250 in small rural hospitals 573,575 . The foregoing demonstrates that infection control staffing can no longer be based on patient census alone, but rather must be determined by the scope of the program, characteristics of the patient population, complexity of the healthcare system, tools available to assist personnel to perform essential tasks (e.g., electronic tracking and laboratory support for surveillance), and unique or urgent needs of the institution and community 552 . Furthermore, appropriate training is required to optimize the quality of work performed 558, 572, 576 .

# II.A.1.a.i. Infection control nurse liaison.
Designating a bedside nurse on a patient care unit as an infection control liaison or "link nurse" is reported to be an effective adjunct to enhance infection control at the unit level  . Such individuals receive training in basic infection control and have frequent communication with the ICPs, but maintain their primary role as bedside caregiver on their units. The infection control nurse liaison increases the awareness of infection control at the unit level. He or she is especially effective in implementation of new policies or control interventions because of the rapport with individuals on the unit, an understanding of unit-specific challenges, and ability to promote strategies that are most likely to be successful in that unit. This position is an adjunct to, not a replacement for, fully trained ICPs. Furthermore, the infection control liaison nurses should not be counted when considering ICP staffing.

# II.A.1.b. Bedside nurse staffing.
There is increasing evidence that the level of bedside nurse-staffing influences the quality of patient care 583,584 . If there are adequate nursing staff, it is more likely that infection control practices, including hand hygiene and Standard and Transmission-Based Precautions, will be given appropriate attention and applied correctly and consistently 552 . A national multicenter study reported strong and consistent inverse relationships between nurse staffing and five adverse outcomes in medical patients, two of which were HAIs: urinary tract infections and pneumonia 583 . The association of nursing staff shortages with increased rates of HAIs has been demonstrated in several outbreaks in hospitals and long term care settings, and with increased transmission of hepatitis C virus in dialysis units 22,418,551, . In most cases, when staffing improved as part of a comprehensive control intervention, the outbreak ended or the HAI rate declined. In two studies 590,596 , the composition of the nursing staff ("pool" or "float" vs. regular staff nurses) influenced the rate of primary bloodstream infections, with an increased infection rate occurring when the proportion of regular nurses decreased and pool nurses increased.

# II.A.1.c. Clinical microbiology laboratory support.
The critical role of the clinical microbiology laboratory in infection control and healthcare epidemiology is described well 553,554, and is supported by the Infectious Disease Society of America policy statement on consolidation of clinical microbiology laboratories published in 2001 553 . The clinical microbiology laboratory contributes to preventing transmission of infectious diseases in healthcare settings by promptly detecting and reporting epidemiologically important organisms, identifying emerging patterns of antimicrobial resistance, and assisting in assessment of the effectiveness of recommended precautions to limit transmission during outbreaks 598 . Outbreaks of infections may be recognized first by laboratorians 162 . Healthcare organizations need to ensure the availability of the recommended scope and quality of laboratory services, a sufficient number of appropriately trained laboratory staff members, and systems to promptly communicate epidemiologically important results to those who will take action (e.g., providers of clinical care, infection control staff, healthcare epidemiologists, and infectious disease consultants) 601 . As concerns about emerging pathogens and bioterrorism grow, the role of the clinical microbiology laboratory takes on even greater importance. For healthcare organizations that outsource microbiology laboratory services (e.g., ambulatory care, home care, LTCFs, smaller acute care hospitals), it is important to specify by contract the types of services (e.g., periodic institution-specific aggregate susceptibility reports) required to support infection control.
Several key functions of the clinical microbiology laboratory are relevant to this guideline:
- Antimicrobial susceptibility by testing and interpretation in accordance with current guidelines developed by the National Committee for Clinical Laboratory Standards (NCCLS), known as the Clinical and Laboratory Standards Institute (CLSI) since 2005 602 , for the detection of emerging resistance patterns 603,604 , and for the preparation, analysis, and distribution of periodic cumulative antimicrobial susceptibility summary reports  . While not required, clinical laboratories ideally should have access to rapid genotypic identification of bacteria and their antibiotic resistance genes 608 .
- Performance of surveillance cultures when appropriate (including retention of isolates for analysis) to assess patterns of infection transmission and effectiveness of infection control interventions at the facility or organization. Microbiologists assist in decisions concerning the indications for initiating and discontinuing active surveillance programs and optimize the use of laboratory resources.
- Molecular typing, on-site or outsourced, in order to investigate and control healthcare-associated outbreaks 609 .
- Application of rapid diagnostic tests to support clinical decisions involving patient treatment, room selection, and implementation of control measures including barrier precautions and use of vaccine or chemoprophylaxis agents (e.g., influenza  , B. pertussis 613 , RSV 614,615 , and enteroviruses 616 ). The microbiologist provides guidance to limit rapid testing to clinical situations in which rapid results influence patient management decisions, as well as providing oversight of point-of-care testing performed by non-laboratory healthcare workers 617 .
- Detection and rapid reporting of epidemiologically important organisms, including those that are reportable to public health agencies.
- Implementation of a quality control program that ensures testing services are appropriate for the population served, and stringently evaluated for sensitivity, specificity, applicability, and feasibility.
- Participation in a multidisciplinary team to develop and maintain an effective institutional program for the judicious use of antimicrobial agents 618,619 .

# II.A.2. Institutional safety culture and organizational characteristics.
Safety culture (or safety climate) refers to a work environment where a shared commitment to safety on the part of management and the workforce is understood and followed 557,620,621 . The authors of the Institute of Medicine Report, To Err is Human 543 , acknowledge that causes of medical error are multifaceted but emphasize repeatedly the pivotal role of system failures and the benefits of a safety culture. A safety culture is created through 1. the actions management takes to improve patient and worker safety; 2. worker participation in safety planning; 3. the availability of appropriate protective equipment; 4. influence of group norms regarding acceptable safety practices; and 5. the organization's socialization process for new personnel.
Safety and patient outcomes can be enhanced by improving or creating organizational characteristics within patient care units as demonstrated by studies of surgical ICUs 622,623 .
Each of these factors has a direct bearing on adherence to transmission prevention recommendations 257 . Measurement of an institutional culture of safety is useful for designing improvements in healthcare 624,625 . Several hospital-based studies have linked measures of safety culture with both employee adherence to safe practices and reduced exposures to blood and body fluids  . One study of hand hygiene practices concluded that improved adherence requires integration of infection control into the organization's safety culture 561 . Several hospitals that are part of the Veterans Administration Healthcare System have taken specific steps toward improving the safety culture, including error reporting mechanisms, performing root cause analysis on problems identified, providing safety incentives, and employee education.  .

# II.A.3. Adherence of healthcare personnel to recommended guidelines.
Adherence to recommended infection control practices decreases transmission of infectious agents in healthcare settings 116,562, . However, several observational studies have shown limited adherence to recommended practices by healthcare personnel 559, . Observed adherence to universal precautions ranged from 43% to 89% 641,642,649,651,652 . However, the degree of adherence depended frequently on the practice that was assessed and, for glove use, the circumstance in which they were used. Appropriate glove use has ranged from a low of 15% 645 to a high of 82% 650 . However, 92% and 98% adherence with glove use have been reported during arterial blood gas collection and resuscitation, respectively, procedures where there may be considerable blood contact 643,656 . Differences in observed adherence have been reported among occupational groups in the same healthcare facility 641 and between experienced and nonexperienced professionals 645 . In surveys of healthcare personnel, self-reported adherence was generally higher than that reported in observational studies. Furthermore, where an observational component was included with a self-reported survey, self-perceived adherence was often greater than observed adherence 657 . Among nurses and physicians, increasing years of experience is a negative predictor of adherence 645,651 . Education to improve adherence is the primary intervention that has been studied. While positive changes in knowledge and attitude have been demonstrated, 640,658 , there often has been limited or no accompanying change in behavior 642,644 . Self-reported adherence is higher in groups that have received an educational intervention 630,659 . Educational interventions that incorporated videotaping and performance feedback were successful in improving adherence during the period of study; the long-term effect of these interventions is not known 654 .The use of videotape also served to identify system problems (e.g., communication and access to personal protective equipment) that otherwise may not have been recognized.
Use of engineering controls and facility design concepts for improving adherence is gaining interest. While introduction of automated sinks had a negative impact on consistent adherence to hand washing 660 , use of electronic monitoring and voice prompts to remind healthcare workers to perform hand hygiene, and improving accessibility to hand hygiene products, increased adherence and contributed to a decrease in HAIs in one study 661 . More information is needed regarding how technology might improve adherence.
Improving adherence to infection control practices requires a multifaceted approach that incorporates continuous assessment of both the individual and the work environment 559, 561 . Using several behavioral theories, Kretzer and Larson concluded that a single intervention (e.g., a handwashing campaign or putting up new posters about transmission precautions) would likely be ineffective in improving healthcare personnel adherence 662 . Improvement requires that the organizational leadership make prevention an institutional priority and integrate infection control practices into the organization's safety culture 561 . A recent review of the literature concluded that variations in organizational factors (e.g., safety climate, policies and procedures, education and training) and individual factors (e.g., knowledge, perceptions of risk, past experience) were determinants of adherence to infection control guidelines for protection against SARS and other respiratory pathogens 257 .

# II.B. Surveillance for Healthcare-Associated Infections (HAIs)
Surveillance is an essential tool for case-finding of single patients or clusters of patients who are infected or colonized with epidemiologically important organisms (e.g., susceptible bacteria such as S. aureus, S. pyogenes  or Enterobacter-Klebsiella spp; MRSA, VRE, and other MDROs; C. difficile; RSV; influenza virus) for which transmission-based precautions may be required. Surveillance is defined as the ongoing, systematic collection, analysis, interpretation, and dissemination of data regarding a health-related event for use in public health action to reduce morbidity and mortality and to improve health 663 . The work of Ignaz Semmelweis that described the role of person-to-person transmission in puerperal sepsis is the earliest example of the use of surveillance data to reduce transmission of infectious agents 664 . Surveillance of both process measures and the infection rates to which they are linked are important for evaluating the effectiveness of infection prevention efforts and identifying indications for change 555,  .
The Study on the Efficacy of Nosocomial Infection Control (SENIC) found that different combinations of infection control practices resulted in reduced rates of nosocomial surgical site infections, pneumonia, urinary tract infections, and bacteremia in acute care hospitals 566 ; however, surveillance was the only component essential for reducing all four types of HAIs. Although a similar study has not been conducted in other healthcare settings, a role for surveillance and the need for novel strategies have been described in LTCFs 398,434,669,670 and in home care  . The essential elements of a surveillance system are: 1. standardized definitions;
2. identification of patient populations at risk for infection; 3. statistical analysis (e.g., risk-adjustment, calculation of rates using appropriate denominators, trend analysis using methods such as statistical process control charts); and 4. feedback of results to the primary caregivers  .
Data gathered through surveillance of high-risk populations, device use, procedures, and/or facility locations (e.g., ICUs) are useful for detecting transmission trends  . Identification of clusters of infections should be followed by a systematic epidemiologic investigation to determine commonalities in persons, places, and time; and guide implementation of interventions and evaluation of the effectiveness of those interventions.
Targeted surveillance based on the highest risk areas or patients has been preferred over facility-wide surveillance for the most effective use of resources 673,676 . However, surveillance for certain epidemiologically important organisms may need to be facilitywide. Surveillance methods will continue to evolve as healthcare delivery systems change 392,677 and user-friendly electronic tools become more widely available for electronic tracking and trend analysis 674,678,679 . Individuals with experience in healthcare epidemiology and infection control should be involved in selecting software packages for data aggregation and analysis to assure that the need for efficient and accurate HAI surveillance will be met. Effective surveillance is increasingly important as legislation requiring public reporting of HAI rates is passed and states work to develop effective systems to support such legislation 680 .

# II.C. Education of HCWs, Patients, and Families
Education and training of healthcare personnel are a prerequisite for ensuring that policies and procedures for Standard and Transmission-Based Precautions are understood and practiced. Understanding the scientific rationale for the precautions will allow HCWs to apply procedures correctly, as well as safely modify precautions based on changing requirements, resources, or healthcare settings 14,655, . In one study, the likelihood of HCWs developing SARS was strongly associated with less than 2 hours of infection control training and lack of understanding of infection control procedures 689 . Education about the important role of vaccines (e.g., influenza, measles, varicella, pertussis, pneumococcal) in protecting healthcare personnel, their patients, and family members can help improve vaccination rates  .
Education on the principles and practices for preventing transmission of infectious agents should begin during training in the health professions and be provided to anyone who has an opportunity for contact with patients or medical equipment (e.g., nursing and medical staff; therapists and technicians, including respiratory, physical, occupational, radiology, and cardiology personnel; phlebotomists; housekeeping and maintenance staff; and students). In healthcare facilities, education and training on Standard and Transmission-Based Precautions are typically provided at the time of orientation and should be repeated as necessary to maintain competency; updated education and training are necessary when policies and procedures are revised or when there is a special circumstance, such as an outbreak that requires modification of current practice or adoption of new recommendations. Education and training materials and methods appropriate to the HCW's level of responsibility, individual learning habits, and language needs, can improve the learning experience 658, .
Education programs for healthcare personnel have been associated with sustained improvement in adherence to best practices and a related decrease in deviceassociated HAIs in teaching and non-teaching settings 639,703  Several studies have shown that, in addition to targeted education to improve specific practices, periodic assessment and feedback of the HCWs knowledge,and adherence to recommended practices are necessary to achieve the desired changes and to identify continuing education needs 562, . Effectiveness of this approach for isolation practices has been demonstrated for control of RSV 116,684 .
Patients, family members, and visitors can be partners in preventing transmission of infections in healthcare settings 9,42, . Information about Standard Precautions, especially hand hygiene, Respiratory Hygiene/Cough Etiquette, vaccination (especially against influenza) and other routine infection prevention strategies may be incorporated into patient information materials that are provided upon admission to the healthcare facility. Additional information about Transmission-Based Precautions is best provided at the time they are initiated. Fact sheets, pamphlets, and other printed material may include information on the rationale for the additional precautions, risks to household members, room assignment for Transmission-Based Precautions purposes, explanation about the use of personal protective equipment by HCWs, and directions for use of such equipment by family members and visitors. Such information may be particularly helpful in the home environment where household members often have primary responsibility for adherence to recommended infection control practices. Healthcare personnel must be available and prepared to explain this material and answer questions as needed.

# II.D. Hand Hygiene
Hand hygiene has been cited frequently as the single most important practice to reduce the transmission of infectious agents in healthcare settings 559,712,713 and is an essential element of Standard Precautions. The term "hand hygiene" includes both handwashing with either plain or antiseptic-containing soap and water, and use of alcohol-based products (gels, rinses, foams) that do not require the use of water. In the absence of visible soiling of hands, approved alcohol-based products for hand disinfection are preferred over antimicrobial or plain soap and water because of their superior microbiocidal activity, reduced drying of the skin, and convenience 559 . Improved hand hygiene practices have been associated with a sustained decrease in the incidence of MRSA and VRE infections primarily in the ICU 561,562, . The scientific rationale, indications, methods, and products for hand hygiene are summarized in other publications 559,717 .
The effectiveness of hand hygiene can be reduced by the type and length of fingernails 559, 718, 719 . Individuals wearing artifical nails have been shown to harbor more pathogenic organisms, especially gram negative bacilli and yeasts, on the nails and in the subungual area than those with native nails 720,721 . In 2002, CDC/HICPAC recommended (Category IA) that artificial fingernails and extenders not be worn by healthcare personnel who have contact with high-risk patients (e.g., those in ICUs, ORs) due to the association with outbreaks of gram-negative bacillus and candidal infections as confirmed by molecular typing of isolates 30,31,559, .The need to restrict the wearing of artificial fingernails by all healthcare personnel who provide direct patient care or by healthcare personnel who have contact with other high risk groups (e.g., oncology, cystic fibrosis patients), has not been studied, but has been recommended by some experts 20 . At this time such decisions are at the discretion of an individual facility's infection control program. There is less evidence that jewelry affects the quality of hand hygiene. Although hand contamination with potential pathogens is increased with ring-wearing 559,726 , no studies have related this practice to HCW-topatient transmission of pathogens.

# II.E. Personal Protective Equipment (PPE) for Healthcare Personnel
PPE refers to a variety of barriers and respirators used alone or in combination to protect mucous membranes, airways, skin, and clothing from contact with infectious agents. The selection of PPE is based on the nature of the patient interaction and/or the likely mode(s) of transmission. Guidance on the use of PPE is discussed in Part III. A suggested procedure for donning and removing PPE that will prevent skin or clothing contamination is presented in the Figure . Designated containers for used disposable or reusable PPE should be placed in a location that is convenient to the site of removal to facilitate disposal and containment of contaminated materials. Hand hygiene is always the final step after removing and disposing of PPE. The following sections highlight the primary uses and methods for selecting this equipment.

# II.E.1. Gloves.
Gloves are used to prevent contamination of healthcare personnel hands when 1. anticipating direct contact with blood or body fluids, mucous membranes, nonintact skin and other potentially infectious material; 2. having direct contact with patients who are colonized or infected with pathogens transmitted by the contact route e.g., VRE, MRSA, RSV 559,727,728 ; or 3. handling or touching visibly or potentially contaminated patient care equipment and environmental surfaces 72,73,559 .
Gloves can protect both patients and healthcare personnel from exposure to infectious material that may be carried on hands 73 . The extent to which gloves will protect healthcare personnel from transmission of bloodborne pathogens (e.g., HIV, HBV, HCV) following a needlestick or other pucture that penetrates the glove barrier has not been determined. Although gloves may reduce the volume of blood on the external surface of a sharp by 46-86% 729 , the residual blood in the lumen of a hollowbore needle would not be affected; therefore, the effect on transmission risk is unknown.
Gloves manufactured for healthcare purposes are subject to FDA evaluation and clearance 730 . Nonsterile disposable medical gloves made of a variety of materials (e.g., latex, vinyl, nitrile) are available for routine patient care 731 . The selection of glove type for non-surgical use is based on a number of factors, including the task that is to be performed, anticipated contact with chemicals and chemotherapeutic agents, latex sensitivity, sizing, and facility policies for creating a latex-free environment 17, . For contact with blood and body fluids during non-surgical patient care, a single pair of gloves generally provides adequate barrier protection 734 . However, there is considerable variability among gloves; both the quality of the manufacturing process and type of material influence their barrier effectiveness 735 . While there is little difference in the barrier properties of unused intact gloves 736 , studies have shown repeatedly that vinyl gloves have higher failure rates than latex or nitrile gloves when tested under simulated and actual clinical conditions 731, . For this reason either latex or nitrile gloves are preferable for clinical procedures that require manual dexterity and/or will involve more than brief patient contact. It may be necessary to stock gloves in several sizes. Heavier, reusable utility gloves are indicated for non-patient care activities, such as handling or cleaning contaminated equipment or surfaces 11,14,739 .
During patient care, transmission of infectious organisms can be reduced by adhering to the principles of working from "clean" to "dirty", and confining or limiting contamination to surfaces that are directly needed for patient care. It may be necessary to change gloves during the care of a single patient to prevent cross-contamination of body sites 559,740 . It also may be necessary to change gloves if the patient interaction also involves touching portable computer keyboards or other mobile equipment that is transported from room to room. Discarding gloves between patients is necessary to prevent transmission of infectious material. Gloves must not be washed for subsequent reuse because microorganisms cannot be removed reliably from glove surfaces and continued glove integrity cannot be ensured. Furthermore, glove reuse has been associated with transmission of MRSA and gram-negative bacilli  .
When gloves are worn in combination with other PPE, they are put on last. Gloves that fit snugly around the wrist are preferred for use with an isolation gown because they will cover the gown cuff and provide a more reliable continuous barrier for the arms, wrists, and hands. Gloves that are removed properly will prevent hand contamination (Figure ).
Hand hygiene following glove removal further ensures that the hands will not carry potentially infectious material that might have penetrated through unrecognized tears or that could contaminate the hands during glove removal 559,728,741 .

# II.E.2. Isolation gowns.
Isolation gowns are used as specified by Standard and Transmission-Based Precautions, to protect the HCW's arms and exposed body areas and prevent contamination of clothing with blood, body fluids, and other potentially infectious material 24,88,262, . The need for and type of isolation gown selected is based on the nature of the patient interaction, including the anticipated degree of contact with infectious material and potential for blood and body fluid penetration of the barrier. The wearing of isolation gowns and other protective apparel is mandated by the OSHA Bloodborne Pathogens Standard 739 . Clinical and laboratory coats or jackets worn over personal clothing for comfort and/or purposes of identity are not considered PPE.
When applying Standard Precautions, an isolation gown is worn only if contact with blood or body fluid is anticipated. However, when Contact Precautions are used (i.e., to prevent transmission of an infectious agent that is not interrupted by Standard Precautions alone and that is associated with environmental contamination), donning of both gown and gloves upon room entry is indicated to address unintentional contact with contaminated environmental surfaces 54,72,73,88 . The routine donning of isolation gowns upon entry into an intensive care unit or other high-risk area does not prevent or influence potential colonization or infection of patients in those areas 365, .
Isolation gowns are always worn in combination with gloves, and with other PPE when indicated. Gowns are usually the first piece of PPE to be donned. Full coverage of the arms and body front, from neck to the mid-thigh or below will ensure that clothing and exposed upper body areas are protected. Several gown sizes should be available in a healthcare facility to ensure appropriate coverage for staff members. Isolation gowns should be removed before leaving the patient care area to prevent possible contamination of the environment outside the patient's room. Isolation gowns should be removed in a manner that prevents contamination of clothing or skin (Figure). The outer, "contaminated", side of the gown is turned inward and rolled into a bundle, and then discarded into a designated container for waste or linen to contain contamination.

# II.E.3. Face protection: masks, goggles, face shields.
II.E.3.a. Masks. Masks are used for three primary purposes in healthcare settings: 1. placed on healthcare personnel to protect them from contact with infectious material from patients e.g., respiratory secretions and sprays of blood or body fluids, consistent with Standard Precautions and Droplet Precautions; 2. placed on healthcare personnel when engaged in procedures requiring sterile technique to protect patients from exposure to infectious agents carried in a healthcare worker's mouth or nose, and 3. placed on coughing patients to limit potential dissemination of infectious respiratory secretions from the patient to others (i.e., Respiratory Hygiene/Cough Etiquette).
Masks may be used in combination with goggles to protect the mouth, nose and eyes, or a face shield may be used instead of a mask and goggles, to provide more complete protection for the face, as discussed below. Masks should not be confused with particulate respirators that are used to prevent inhalation of small particles that may contain infectious agents transmitted via the airborne route as described below.
The mucous membranes of the mouth, nose, and eyes are susceptible portals of entry for infectious agents, as can be other skin surfaces if skin integrity is compromised (e.g., by acne, dermatitis) 66, . Therefore, use of PPE to protect these body sites is an important component of Standard Precautions. The protective effect of masks for exposed healthcare personnel has been demonstrated 93,113,755,756 . Procedures that generate splashes or sprays of blood, body fluids, secretions, or excretions (e.g., endotracheal suctioning, bronchoscopy, invasive vascular procedures) require either a face shield (disposable or reusable) or mask and goggles 93-95, 96, 113, 115, 262, 739, 757 .The wearing of masks, eye protection, and face shields in specified circumstances when blood or body fluid exposures are likely to occur is mandated by the OSHA Bloodborne Pathogens Standard 739 . Appropriate PPE should be selected based on the anticipated level of exposure.
Two mask types are available for use in healthcare settings: surgical masks that are cleared by the FDA and required to have fluid-resistant properties, and procedure or isolation masks 758 #2688 . No studies have been published that compare mask types to determine whether one mask type provides better protection than another. Since procedure/isolation masks are not regulated by the FDA, there may be more variability in quality and performance than with surgical masks. Masks come in various shapes (e.g., molded and non-molded), sizes, filtration efficiency, and method of attachment (e.g., ties, elastic, ear loops). Healthcare facilities may find that different types of masks are needed to meet individual healthcare personnel needs.

# II.E.3.b. Goggles, face shields.
Guidance on eye protection for infection control has been published 759 . The eye protection chosen for specific work situations (e.g., goggles or face shield) depends upon the circumstances of exposure, other PPE used, and personal vision needs. Personal eyeglasses and contact lenses are NOT considered adequate eye protection (NIOSH Eye Protection for Infection Control () ). NIOSH states that, eye protection must be comfortable, allow for sufficient peripheral vision, and must be adjustable to ensure a secure fit. It may be necessary to provide several different types, styles, and sizes of protective equipment. Indirectly-vented goggles with a manufacturer's anti-fog coating may provide the most reliable practical eye protection from splashes, sprays, and respiratory droplets from multiple angles. Newer styles of goggles may provide better indirect airflow properties to reduce fogging, as well as better peripheral vision and more size options for fitting goggles to different workers. Many styles of goggles fit adequately over prescription glasses with minimal gaps. While effective as eye protection, goggles do not provide splash or spray protection to other parts of the face.
The role of goggles, in addition to a mask, in preventing exposure to infectious agents transmitted via respiratory droplets has been studied only for RSV. Reports published in the mid-1980s demonstrated that eye protection reduced occupational transmission of RSV 760,761 . Whether this was due to preventing hand-eye contact or respiratory droplet-eye contact has not been determined. However, subsequent studies demonstrated that RSV transmission is effectively prevented by adherence to Standard plus Contact Precations and that for this virus routine use of goggles is not necessary 24,116,117,684,762 . It is important to remind healthcare personnel that even if Droplet Precautions are not recommended for a specific respiratory tract pathogen, protection for the eyes, nose and mouth by using a mask and goggles, or face shield alone, is necessary when it is likely that there will be a splash or spray of any respiratory secretions or other body fluids as defined in Standard Precautions.
Disposable or non-disposable face shields may be used as an alternative to goggles 759 . As compared with goggles, a face shield can provide protection to other facial areas in addition to the eyes. Face shields extending from chin to crown provide better face and eye protection from splashes and sprays; face shields that wrap around the sides may reduce splashes around the edge of the shield.
Removal of a face shield, goggles and mask can be performed safely after gloves have been removed, and hand hygiene performed. The ties, ear pieces and/or headband used to secure the equipment to the head are considered "clean" and therefore safe to touch with bare hands. The front of a mask, goggles and face shield are considered contaminated (Figure ).

# II.E.4. Respiratory protection.
The subject of respiratory protection as it applies to preventing transmission of airborne infectious agents, including the need for and frequency of fit-testing is under scientific review and was the subject of a CDC workshop in 2004 763 . Respiratory protection currently requires the use of a respirator with N95 or higher filtration to prevent inhalation of infectious particles. Information about respirators and respiratory protection programs is summarized in the Guideline for Preventing Transmission of Mycobacterium tuberculosis in Health-care Settings, 2005 (CDC.MMWR 2005; 54: RR-17 12 ).
Respiratory protection is broadly regulated by OSHA under the general industry standard for respiratory protection (29CFR1910.134) 764 which requires that U.S. employers in all employment settings implement a program to protect employees from inhalation of toxic materials. OSHA program components include medical clearance to wear a respirator; provision and use of appropriate respirators, including fit-tested NIOSH-certified N95 and higher particulate filtering respirators; education on respirator use and periodic reevaluation of the respiratory protection program. When selecting particulate respirators, models with inherently good fit characteristics (i.e., those expected to provide protection factors of 10 or more to 95% of wearers) are preferred and could theoretically relieve the need for fit testing 765,766 . Issues pertaining to respiratory protection remain the subject of ongoing debate. Information on various types of respirators may be found at  and in published studies 765,767,768 . A user-seal check (formerly called a "fit check") should be performed by the wearer of a respirator each time a respirator is donned to minimize air leakage around the facepiece 769 . The optimal frequency of fit-testng has not been determined; re-testing may be indicated if there is a change in facial features of the wearer, onset of a medical condition that would affect respiratory function in the wearer, or a change in the model or size of the initially assigned respirator 12 .
Respiratory protection was first recommended for protection of preventing U.S. healthcare personnel from exposure to M. tuberculosis in 1989. That recommendation has been maintained in two successive revisions of the Guidelines for Prevention of Transmission of Tuberculosis in Hospitals and other Healthcare Settings 12,126 . The incremental benefit from respirator use, in addition to administrative and engineering controls (i.e., AIIRs, early recognition of patients likely to have tuberculosis and prompt placement in an AIIR, and maintenance of a patient with suspected tuberculosis in an AIIR until no longer infectious), for preventing transmission of airborne infectious agents (e.g., M. tuberculosis) is undetermined. Although some studies have demonstrated effective prevention of M. tuberculosis transmission in hospitals where surgical masks, instead of respirators, were used in conjunction with other administrative and engineering controls 637,770,771 , CDC currently recommends N95 or higher level respirators for personnel exposed to patients with suspected or confirmed tuberculosis. Currently this is also true for other diseases that could be transmitted through the airborne route, including SARS 262 and smallpox 108,129,772 , until inhalational transmission is better defined or healthcare-specific protective equipment more suitable for for preventing infection are developed. Respirators are also currently recommended to be worn during the performance of aerosol-generating procedures (e.g., intubation, bronchoscopy, suctioning) on patients withSARS Co-V infection, avian influenza and pandemic influenza (See Appendix A).
Although Airborne Precautions are recommended for preventing airborne transmission of measles and varicella-zoster viruses, there are no data upon which to base a recommendation for respiratory protection to protect susceptible personnel against these two infections; transmission of varicella-zoster virus has been prevented among pediatric patients using negative pressure isolation alone 773 . Whether respiratory protection (i.e., wearing a particulate respirator) would enhance protection from these viruses has not been studied. Since the majority of healthcare personnel have natural or acquired immunity to these viruses, only immune personnel generally care for patients with these infections  . Although there is no evidence to suggest that masks are not adequate to protect healthcare personnel in these settings, for purposes of consistency and simplicity, or because of difficulties in ascertaining immunity, some facilities may require the use of respirators for entry into all AIIRs, regardless of the specific infectious agent.
Procedures for safe removal of respirators are provided (Figure). In some healthcare settings, particulate respirators used to provide care for patients with M. tuberculosis are reused by the same HCW. This is an acceptable practice providing the respirator is not damaged or soiled, the fit is not compromised by change in shape, and the respirator has not been contaminated with blood or body fluids. There are no data on which to base a recommendation for the length of time a respirator may be reused.

# II.F. control nurse per 250 beds, were associated with a 32%re to Bloodborne Pathogens

# II.F.1. Prevention of needlesticks and other sharps-related injuries.
Injuries due to needles and other sharps have been associated with transmission of HBV, HCV and HIV to healthcare personnel 778,779 . The prevention of sharps injuries has always been an essential element of Universal and now Standard Precautions 1, 780 . These include measures to handle needles and other sharp devices in a manner that will prevent injury to the user and to others who may encounter the device during or after a procedure. These measures apply to routine patient care and do not address the prevention of sharps injuries and other blood exposures during surgical and other invasive procedures that are addressed elsewhere  .
Since 1991, when OSHA first issued its Bloodborne Pathogens Standard to protect healthcare personnel from blood exposure, the focus of regulatory and legislative activity has been on implementing a hierarchy of control measures. This has included focusing attention on removing sharps hazards through the development and use of engineering controls. The federal Needlestick Safety and Prevention Act signed into law in November, 2000 authorized OSHA's revision of its Bloodborne Pathogens Standard to more explicitly require the use of safety-engineered sharp devices 786 . CDC has provided guidance on sharps injury prevention 787,788 , including for the design, implementation and evaluation of a comprehensive sharps injury prevention program 789 .

# II.F.2. Prevention of mucous membrane contact.
Exposure of mucous membranes of the eyes, nose and mouth to blood and body fluids has been associated with the transmission of bloodborne viruses and other infectious agents to healthcare personnel 66, 752, 754, 779 . The prevention of mucous membrane exposures has always been an element of Universal and now Standard Precautions for routine patient care 1, 753 and is subject to OSHA bloodborne pathogen regulations. Safe work practices, in addition to wearing PPE, are used to protect mucous membranes and non-intact skin from contact with potentially infectious material. These include keeping gloved and ungloved hands that are contaminated from touching the mouth, nose, eyes, or face; and positioning patients to direct sprays and splatter away from the face of the caregiver. Careful placement of PPE before patient contact will help avoid the need to make PPE adjustments and possible face or mucous membrane contamination during use.
In areas where the need for resuscitation is unpredictable, mouthpieces, pocket resuscitation masks with one-way valves, and other ventilation devices provide an alternative to mouth-to-mouth resuscitation, preventing exposure of the caregiver's nose and mouth to oral and respiratory fluids during the procedure.

# II.F.2.a. Precautions during aerosol-generating procedures.
The performance of procedures that can generate small particle aerosols (aerosol-generating procedures), such as bronchoscopy, endotracheal intubation, and open suctioning of the respiratory tract, have been associated with transmission of infectious agents to healthcare personnel, including M. tuberculosis 790 , SARS-CoV 93,94,98 and N. meningitidis 95 . Protection of the eyes, nose and mouth, in addition to gown and gloves, is recommended during performance of these procedures in accordance with Standard Precautions. Use of a particulate respirator is recommended during aerosol-generating procedures when the aerosol is likely to contain M. tuberculosis, SARS-CoV, or avian or pandemic influenza viruses.

# II.G. Patient Placement

# II.G.1. Hospitals and long-term care settings.
Options for patient placement include single patient rooms, two patient rooms, and multi-bed wards. Of these, single patient rooms are prefered when there is a concern about transmission of an infectious agent.
Although some studies have failed to demonstrate the efficacy of single patient rooms to prevent HAIs 791 , other published studies, including one commissioned by the American Institute of Architects and the Facility Guidelines Institute, have documented a beneficial relationship between private rooms and reduction in infectious and noninfectious adverse patient outcomes 792,793 . The AIA notes that private rooms are the trend in hospital planning and design. However, most hospitals and long-term care facilities have multi-bed rooms and must consider many competing priorities when determining the appropriate room placement for patients (e.g., reason for admission; patient characteristics, such as age, gender, mental status; staffing needs; family requests; psychosocial factors; reimbursement concerns). In the absence of obvious infectious diseases that require specified airborne infection isolation rooms (e.g., tuberculosis, SARS, chickenpox), the risk of transmission of infectious agents is not always considered when making placement decisions.
When there are only a limited number of single-patient rooms, it is prudent to prioritize them for those patients who have conditions that facilitate transmission of infectious material to other patients (e.g., draining wounds, stool incontinence, uncontained secretions) and for those who are at increased risk of acquisition and adverse outcomes resulting from HAI (e.g., immunosuppression, open wounds, indwelling catheters, anticipated prolonged length of stay, total dependence on HCWs for activities of daily living) 15,24,43,430,794,795 .
Single-patient rooms are always indicated for patients placed on Airborne Precautions and in a Protective Environment and are preferred for patients who require Contact or Droplet Precautions 23,24,410,435,796,797 . During a suspected or proven outbreak caused by a pathogen whose reservoir is the gastrointestinal tract, use of single patient rooms with private bathrooms limits opportunities for transmission, especially when the colonized or infected patient has poor personal hygiene habits, fecal incontinence, or cannot be expected to assist in maintaining procedures that prevent transmission of microorganisms (e.g., infants, children, and patients with altered mental status or developmental delay). In the absence of continued transmission, it is not necessary to provide a private bathroom for patients colonized or infected with enteric pathogens as long as personal hygiene practices and Standard Precautions, especially hand hygiene and appropriate environmental cleaning, are maintained. Assignment of a dedicated commode to a patient,and cleaning and disinfecting fixtures and equipment that may have fecal contamination (e.g., bathrooms, commodes 798 , scales used for weighing diapers) and the adjacent surfaces with appropriate agents may be especially important when a singlepatient room can not be used since environmental contamination with intestinal tract pathogens is likely from both continent and incontinent patients 54,799 . Results of several studies to determine the benefit of a single-patient room to prevent transmission of Clostridium difficile are inconclusive 167, . Some studies have shown that being in the same room with a colonized or infected patient is not necessarily a risk factor for transmission 791, . However, for children, the risk of healthcare-associated diarrhea is increased with the increased number of patients per room 806 . Thus, patient factors are important determinants of infection transmission risks, and the need for a single-patient room and/or private bathroom for any patient is best determined on a case-by-case basis.
Cohorting is the practice of grouping together patients who are colonized or infected with the same organism to confine their care to one area and prevent contact with other patients. Cohorts are created based on clinical diagnosis, microbiologic confirmation when available, epidemiology, and mode of transmission of the infectious agent. It is generally preferred not to place severely immunosuppressed patients in rooms with other patients. Cohorting has been used extensively for managing outbreaks of MDROs including MRSA 22,807 , VRE 638,808,809 , MDR-ESBLs 810 ; Pseudomonas aeruginosa 29 ; methicillin-susceptible Staphylococcus aureus 811 ; RSV 812,813 ; adenovirus keratoconjunctivitis 814 ; rotavirus 815 ; and SARS 816 . Modeling studies provide additional support for cohorting patients to control outbreaks Talon  . However, cohorting often is implemented only after routine infection control measures have failed to control an outbreak.
Assigning or cohorting healthcare personnel to care only for patients infected or colonized with a single target pathogen limits further transmission of the target pathogen to uninfected patients 740,819 but is difficult to achieve in the face of current staffing shortages in hospitals 583 and residential healthcare sites  . However, when continued transmission is occurring after implementing routine infection control measures and creating patient cohorts, cohorting of healthcare personnel may be beneficial.
During the seasons when RSV, human metapneumovirus 823 , parainfluenza, influenza, other respiratory viruses 824 , and rotavirus are circulating in the community, cohorting based on the presenting clinical syndrome is often a priority in facilities that care for infants and young children 825 . For example, during the respiratory virus season, infants may be cohorted based soley on the clinical diagnosis of bronchiolitis due to the logistical difficulties and costs associated with requiring microbiologic confirmation prior to room placement, and the predominance of RSV during most of the season. However, when available, single patient rooms are always preferred since a common clinical presentation (e.g., bronchiolitis), can be caused by more than one infectious agent 823,824,826 . Furthermore, the inability of infants and children to contain body fluids, and the close physical contact that occurs during their care, increases infection transmission risks for patients and personnel in this setting 24,795 .

# II.G.2. Ambulatory settings.
Patients actively infected with or incubating transmissible infectious diseases are seen frequently in ambulatory settings (e.g., outpatient clinics, physicians' offices, emergency departments) and potentially expose healthcare personnel and other patients, family members and visitors 21,34,127,135,142,827 . In response to the global outbreak of SARS in 2003 and in preparation for pandemic influenza, healthcare providers working in outpatient settings are urged to implement source containment measures (e.g., asking couging patients to wear a surgical mask or cover their coughs with tissues) to prevent transmission of respiratory infections, beginning at the point of initial patient encounter 9,262,828 as described below in section III.A.1.a. Signs can be posted at the entrance to facilities or at the reception or registration desk requesting that the patient or individuals accompanying the patient promptly inform the receptionist if there are symptoms of a respiratory infection (e.g., cough, flu-like illness, increased production of respiratory secretions). The presence of diarrhea, skin rash, or known or suspected exposure to a transmissible disease (e.g., measles, pertussis, chickenpox, tuberculosis) also could be added. Placement of potentially infectious patients without delay in an examination room limits the number of exposed individuals, e.g., in the common waiting area.
In waiting areas, maintaining a distance between symptomatic and non-symptomatic patients (e.g., >3 feet), in addition to source control measures, may limit exposures. However, infections transmitted via the airborne route (e.g., M tuberculosis, measles, chickenpox) require additional precautions 12,125,829 . Patients suspected of having such an infection can wear a surgical mask for source containment, if tolerated, and should be placed in an examination room, preferably an AIIR, as soon as possible. If this is not possible, having the patient wear a mask and segregate him/herself from other patients in the waiting area will reduce opportunities to expose others. Since the person(s) accompanying the patient also may be infectious, application of the same infection control precautions may need to be extended to these persons if they are symptomatic 21, 252, 830 . For example, family members accompanying children admitted with suspected M. tuberculosis have been found to have unsuspected pulmonary tuberculosis with cavitary lesions, even when asymptomatic 42,831 .
Patients with underlying conditions that increase their susceptibility to infection (e.g., those who are immunocompromised 43,44 or have cystic fibrosis 20 ) require special efforts to protect them from exposures to infected patients in common waiting areas. By informing the receptionist of their infection risk upon arrival, appropriate steps may be taken to further protect them from infection. In some cystic fibrosis clinics, in order to avoid exposure to other patients who could be colonized with B. cepacia, patients have been given beepers upon registration so that they may leave the area and receive notification to return when an examination room becomes available 832 .

# II.G.3. Home care.
In home care, the patient placement concerns focus on protecting others in the home from exposure to an infectious household member. For individuals who are especially vulnerable to adverse outcomes associated with certain infections, it may be beneficial to either remove them from the home or segregate them within the home. Persons who are not part of the household may need to be prohibited from visiting during the period of infectivity. For example, if a patient with pulmonary tuberculosis is contagious and being cared for at home, very young children (<4 years of age) 833 and immunocompromised persons who have not yet been infected should be removed or excluded from the household. During the SARS outbreak of 2003, segregation of infected persons during the communicable phase of the illness was beneficial in preventing household transmission 249,834 .

# II.H. Transport of Patients
Several principles are used to guide transport of patients requiring Transmission-Based Precautions. In the inpatient and residential settings these include 1. limiting transport of such patients to essential purposes, such as diagnostic and therapeutic procedures that cannot be performed in the patient's room; 2. when transport is necessary, using appropriate barriers on the patient (e.g., mask, gown, wrapping in sheets or use of impervious dressings to cover the affected area(s) when infectious skin lesions or drainage are present, consistent with the route and risk of transmission; 3. notifying healthcare personnel in the receiving area of the impending arrival of the patient and of the precautions necessary to prevent transmission; and 4. for patients being transported outside the facility, informing the receiving facility and the medi-van or emergency vehicle personnel in advance about the type of Transmission-Based Precautions being used.
For tuberculosis, additional precautions may be needed in a small shared air space such as in an ambulance 12 .

# II.I. Environmental Measures
Cleaning and disinfecting non-critical surfaces in patient-care areas are part of Standard Precautions. In general, these procedures do not need to be changed for patients on Transmission-Based Precautions. The cleaning and disinfection of all patient-care areas is important for frequently touched surfaces, especially those closest to the patient, that are most likely to be contaminated (e.g., bedrails, bedside tables, commodes, doorknobs, sinks, surfaces and equipment in close proximity to the patient) 11,72,73,835 .
The frequency or intensity of cleaning may need to change based on the patient's level of hygiene and the degree of environmental contamination and for certain for infectious agents whose reservoir is the intestinal tract 54 . This may be especially true in LTCFs and pediatric facilities where patients with stool and urine incontinence are encountered more frequently. Also, increased frequency of cleaning may be needed in a Protective Environment to minimize dust accumulation 11 . Special recommendations for cleaning and disinfecting environmental surfaces in dialysis centers have been published 18 . In all healthcare settings, administrative, staffing and scheduling activities should prioritize the proper cleaning and disinfection of surfaces that could be implicated in transmission.
During a suspected or proven outbreak where an environmental reservoir is suspected, routine cleaning procedures should be reviewed, and the need for additional trained cleaning staff should be assessed. Adherence should be monitored and reinforced to promote consistent and correct cleaning is performed.
EPA-registered disinfectants or detergents/disinfectants that best meet the overall needs of the healthcare facility for routine cleaning and disinfection should be selected 11,836 . In general, use of the existing facility detergent/disinfectant according to the manufacturer's recommendations for amount, dilution, and contact time is sufficient to remove pathogens from surfaces of rooms where colonized or infected individuals were housed. This includes those pathogens that are resistant to multiple classes of antimicrobial agents (e.g., C. difficile, VRE, MRSA, MDR-GNB 11,24,88,435,746,796,837 ). Most often, environmental reservoirs of pathogens during outbreaks are related to a failure to follow recommended procedures for cleaning and disinfection rather than the specific cleaning and disinfectant agents used  .
Certain pathogens (e.g., rotavirus, noroviruses, C. difficile) may be resistant to some routinely used hospital disinfectants 275,292, .The role of specific disinfectants in limiting transmission of rotavirus has been demonstrated experimentally 842 . Also, since C. difficile may display increased levels of spore production when exposed to nonchlorine-based cleaning agents, and the spores are more resistant than vegetative cells to commonly used surface disinfectants, some investigators have recommended the use of a 1:10 dilution of 5.25% sodium hypochlorite (household bleach) and water for routine environmental disinfection of rooms of patients with C. difficile when there is continued transmission 844,848 . In one study, the use of a hypochlorite solution was associated with a decrease in rates of C. difficile infections 847 . The need to change disinfectants based on the presence of these organisms can be determined in consultation with the infection control committee 11,847,848 .
Detailed recommendations for disinfection and sterilization of surfaces and medical equipment that have been in contact with prion-containing tissue or high risk body fluids, and for cleaning of blood and body substance spills, are available in the Guidelines for Environmental Infection Control in Health-Care Facilities 11 and in the Guideline for Disinfection and Sterilization 848 .

# II.J. Patient Care Equipment and Instruments/Devices
Medical equipment and instruments/devices must be cleaned and maintained according to the manufacturers' instructions to prevent patient-to-patient transmission of infectious agents 86,87,325,849 . Cleaning to remove organic material must always precede high level disinfection and sterilization of critical and semi-critical instruments and devices because residual proteinacous material reduces the effectiveness of the disinfection and sterilization processes 836,848 . Noncritical equipment, such as commodes, intravenous pumps, and ventilators, must be thoroughly cleaned and disinfected before use on another patient. All such equipment and devices should be handled in a manner that will prevent HCW and environmental contact with potentially infectious material. It is important to include computers and personal digital assistants (PDAs) used in patient care in policies for cleaning and disinfection of non-critical items. The literature on contamination of computers with pathogens has been summarized 850 and two reports have linked computer contamination to colonization and infections in patients 851,852 .
Although keyboard covers and washable keyboards that can be easily disinfected are in use, the infection control benefit of those items and optimal management have not been determined.
In all healthcare settings, providing patients who are on Transmission-Based Precautions with dedicated noncritical medical equipment (e.g., stethoscope, blood pressure cuff, electronic thermometer) has been beneficial for preventing transmission 74,89,740,853,854 . When this is not possible, disinfection after use is recommended. Consult other guidelines for detailed guidance in developing specific protocols for cleaning and reprocessing medical equipment and patient care items in both routine and special circumstances 11,14,18,20,740,836,848 .
In home care, it is preferable to remove visible blood or body fluids from durable medical equipment before it leaves the home. Equipment can be cleaned on-site using a detergent/disinfectant and, when possible, should be placed in a single plastic bag for transport to the reprocessing location 20,739 .

# II.K. Textiles and Laundry
Soiled textiles, including bedding, towels, and patient or resident clothing may be contaminated with pathogenic microorganisms. However, the risk of disease transmission is negligible if they are handled, transported, and laundered in a safe manner 11,855,856 . Key principles for handling soiled laundry are 1. not shaking the items or handling them in any way that may aerosolize infectious agents; 2. avoiding contact of one's body and personal clothing with the soiled items being handled; and 3. containing soiled items in a laundry bag or designated bin. When laundry chutes are used, they must be maintained to minimize dispersion of aerosols from contaminated items 11 .
The methods for handling, transporting, and laundering soiled textiles are determined by organizational policy and any applicable regulations 739 ; guidance is provided in the Guidelines for Environmental Infection Control 11 . Rather than rigid rules and regulations, hygienic and common sense storage and processing of clean textiles is recommended 11,857 . When laundering occurs outside of a healthcare facility, the clean items must be packaged or completely covered and placed in an enclosed space during transport to prevent contamination with outside air or construction dust that could contain infectious fungal spores that are a risk for immunocompromised patients 11 .
Institutions are required to launder garments used as personal protective equipment and uniforms visibly soiled with blood or infective material 739 . There are few data to determine the safety of home laundering of HCW uniforms, but no increase in infection rates was observed in the one published study 858 and no pathogens were recovered from home-or hospital-laundered scrubs in another study 859 . In the home, textiles and laundry from patients with potentially transmissible infectious pathogens do not require special handling or separate laundering, and may be washed with warm water and detergent 11,858,859 .

# II.L. Solid Waste
The management of solid waste emanating from the healthcare environment is subject to federal and state regulations for medical and non-medical waste 860,861 . No additional precautions are needed for non-medical solid waste that is being removed from rooms of patients on Transmission-Based Precautions. Solid waste may be contained in a single bag (as compared to using two bags) of sufficient strength. 862

# II.M. Dishware and Eating Utensils
The combination of hot water and detergents used in dishwashers is sufficient to decontaminate dishware and eating utensils. Therefore, no special precautions are needed for dishware (e.g., dishes, glasses, cups) or eating utensils; reusable dishware and utensils may be used for patients requiring Transmission-Based Precautions. In the home and other communal settings, eating utensils and drinking vessels that are being used should not be shared, consistent with principles of good personal hygiene and for the purpose of preventing transmission of respiratory viruses, Herpes simplex virus, and infectious agents that infect the gastrointestinal tract and are transmitted by the fecal/oral route (e.g., hepatitis A virus, noroviruses). If adequate resources for cleaning utensils and dishes are not available, disposable products may be used.

# II.N. Adjunctive Measures
Important adjunctive measures that are not considered primary components of programs to prevent transmission of infectious agents, but improve the effectiveness of such programs, include 1. antimicrobial management programs; 2. postexposure chemoprophylaxis with antiviral or antibacterial agents; 3. vaccines used both for pre and postexposure prevention; and 4. screening and restricting visitors with signs of transmissible infections.
Detailed discussion of judicious use of antimicrobial agents is beyond the scope of this document; however the topic is addressed in the Management of Multidrug-Resistant Organisms in Healthcare Settings 2006 (/).

# II.N.1. Chemoprophylaxis.
Antimicrobial agents and topical antiseptics may be used to prevent infection and potential outbreaks of selected agents. Infections for which postexposure chemoprophylaxis is recommended under defined conditions include B. pertussis 17,863 , N. meningitidis 864 , B. anthracis after environmental exposure to aeosolizable material 865 , influenza virus 611 , HIV 866 , and group A streptococcus 160 . Orally administered antimicrobials may also be used under defined circumstances for MRSA decolonization of patients or healthcare personnel 867 .
Another form of chemoprophylaxis is the use of topical antiseptic agents. For example, triple dye is used routinely on the umbilical cords of term newborns to reduce the risk of colonization, skin infections, and omphalitis caused by S. aureus, including MRSA, and group A streptococcus 868,869 . Extension of the use of triple dye to low birth weight infants in the NICU was one component of a program that controlled one longstanding MRSA outbreak 22 . Topical antiseptics are also used for decolonization of healthcare personnel or selected patients colonized with MRSA, using mupirocin as discussed in the MDRO guideline 870 867, 871-873 .

# II.N.2. Immunoprophylaxis.
Certain immunizations recommended for susceptible healthcare personnel have decreased the risk of infection and the potential for transmission in healthcare facilities 17,874 . The OSHA mandate that requires employers to offer hepatitis B vaccination to HCWs played a substantial role in the sharp decline in incidence of occupational HBV infection 778,875 . The use of varicella vaccine in healthcare personnel has decreased the need to place susceptible HCWs on administrative leave following exposure to patients with varicella 775 . Also, reports of healthcare-associated transmission of rubella in obstetrical clinics 33,876 and measles in acute care settings 34 demonstrate the importance of immunization of susceptible healthcare personnel against childhood diseases. Many states have requirements for HCW vaccination for measles and rubella in the absence of evidence of immunity. Annual influenza vaccine campaigns targeted to patients and healthcare personnel in LTCFs and acute-care settings have been instrumental in preventing or limiting institutional outbreaks and increasing attention is being directed toward improving influenza vaccination rates in healthcare personnel 35,611,690,877,878,879 .
Transmission of B. pertussis in healthcare facilities has been associated with large and costly outbreaks that include both healthcare personnel and patients 17,36,41,100,683,827,880,881 . HCWs who have close contact with infants with pertussis are at particularly high risk because of waning immunity and, until 2005, the absence of a vaccine that could be used in adults. However, two acellular pertussis vaccines were licensed in the United States in 2005, one for use in individuals aged 11-18 and one for use in ages 10-64 years 882 . Provisional ACIP recommendations at the time of publication of this document include adolescents and adults, especially those with contact with infants < 12 months of age and healthcare personnel with direct patient contact 883 884 .
Immunization of children and adults will help prevent the introduction of vaccinepreventable diseases into healthcare settings. The recommended immunization schedule for children is published annually in the January issues of the Morbidity Mortality Weekly Report with interim updates as needed 885,886 . An adult immunization schedule also is available for healthy adults and those with special immunization needs due to high risk medical conditions 887 .
Some vaccines are also used for postexposure prophylaxis of susceptible individuals, including varicella 888 , influenza 611 , hepatitis B 778 , and smallpox 225 vaccines 17,874 . In the future, administration of a newly developed S. aureus conjugate vaccine (still under investigation) to selected patients may provide a novel method of preventing healthcareassociated S. aureus, including MRSA, infections in high-risk groups (e.g., hemodialysis patients and candidates for selected surgical procedures) 889,890 .
Immune globulin preparations also are used for postexposure prophylaxis of certain infectious agents under specified circumstances (e.g., varicella-zoster virus , hepatitis B virus , rabies , measles and hepatitis A virus  17,833,874 ). The RSV monoclonal antibody preparation, Palivizumab, may have contributed to controlling a nosocomial outbreak of RSV in one NICU, but there is insufficient evidence to support a routine recommendation for its use in this setting 891 .

# II.N. 3. Management of visitors.

# II.N.3.a. Visitors as sources of infection.
Visitors have been identified as the source of several types of HAIs (e.g., pertussis 40,41 , M. tuberculosis 42,892 , influenza, and other respiratory viruses 24,43,44,373 and SARS 21, ). However, effective methods for visitor screening in healthcare settings have not been studied. Visitor screening is especially important during community outbreaks of infectious diseases and for high risk patient units. Sibling visits are often encouraged in birthing centers, post partum rooms and in pediatric inpatient units, ICUs, and in residential settings for children; in hospital settings, a child visitor should visit only his or her own sibling. Screening of visiting siblings and other children before they are allowed into clinical areas is necessary to prevent the introduction of childhood illnesses and common respiratory infections. Screening may be passive through the use of signs to alert family members and visitors with signs and symptoms of communicable diseases not to enter clinical areas. More active screening may include the completion of a screening tool or questionnaire which elicits information related to recent exposures or current symptoms. That information is reviewed by the facility staff and the visitor is either permitted to visit or is excluded 833 .
Family and household members visiting pediatric patients with pertussis and tuberculosis may need to be screened for a history of exposure as well as signs and symptoms of current infection. Potentially infectious visitors are excluded until they receive appropriate medical screening, diagnosis, or treatment. If exclusion is not considered to be in the best interest of the patient or family (i.e., primary family members of critically or terminally ill patients), then the symptomatic visitor must wear a mask while in the healthcare facility and remain in the patient's room, avoiding exposure to others, especially in public waiting areas and the cafeteria.
Visitor screening is used consistently on HSCT units 15,43 . However, considering the experience during the 2003 SARS outbreaks and the potential for pandemic influenza, developing effective visitor screening systems will be beneficial 9 . Education concerning Respiratory Hygiene/Cough Etiquette is a useful adjunct to visitor screening.

# II.N.3.b. Use of barrier precautions by visitors.
The use of gowns, gloves, or masks by visitors in healthcare settings has not been addressed specifically in the scientific literature. Some studies included the use of gowns and gloves by visitors in the control of MDRO's, but did not perform a separate analysis to determine whether their use by visitors had a measurable impact  . Family members or visitors who are providing care or having very close patient contact (e.g., feeding, holding) may have contact with other patients and could contribute to transmission if barrier precautions are not used correctly. Specific recommendations may vary by facility or by unit and should be determined by the level of interaction.

# Part III: Precautions to Prevent Transmission of Infectious Agents
There are two tiers of HICPAC/CDC precautions to prevent transmission of infectious agents, Standard Precautions and Transmission-Based Precautions. Standard Precautions are intended to be applied to the care of all patients in all healthcare settings, regardless of the suspected or confirmed presence of an infectious agent. Implementation of Standard Precautions constitutes the primary strategy for the prevention of healthcare-associated transmission of infectious agents among patients and healthcare personnel. Transmission-Based Precautions are for patients who are known or suspected to be infected or colonized with infectious agents, including certain epidemiologically important pathogens, which require additional control measures to effectively prevent transmission. Since the infecting agent often is not known at the time of admission to a healthcare facility, Transmission-Based Precautions are used empirically, according to the clinical syndrome and the likely etiologic agents at the time, and then modified when the pathogen is identified or a transmissible infectious etiology is ruled out. Examples of this syndromic approach are presented in Table 2. The HICPAC/CDC Guidelines also include recommendations for creating a Protective Environment for allogeneic HSCT patients.  4 and 5 for summaries of the key elements of these sets of precautions

# III.A. Standard Precautions Standard Precautions combine the major features of
Universal Precautions (UP) 780,896 and Body Substance Isolation (BSI) 640 and are based on the principle that all blood, body fluids, secretions, excretions except sweat, nonintact skin, and mucous membranes may contain transmissible infectious agents. Standard Precautions include a group of infection prevention practices that apply to all patients, regardless of suspected or confirmed infection status, in any setting in which healthcare is delivered (Table 4). These include: hand hygiene; use of gloves, gown, mask, eye protection, or face shield, depending on the anticipated exposure; and safe injection practices. Also, equipment or items in the patient environment likely to have been contaminated with infectious body fluids must be handled in a manner to prevent transmission of infectious agents (e.g., wear gloves for direct contact, contain heavily soiled equipment, properly clean and disinfect or sterilize reusable equipment before use on another patient).
The application of Standard Precautions during patient care is determined by the nature of the HCW-patient interaction and the extent of anticipated blood, body fluid, or pathogen exposure. For some interactions (e.g., performing venipuncture), only gloves may be needed; during other interactions (e.g., intubation), use of gloves, gown, and face shield or mask and goggles is necessary. Education and training on the principles and rationale for recommended practices are critical elements of Standard Precautions because they facilitate appropriate decision-making and promote adherence when HCWs are faced with new circumstances 655, . An example of the importance of the use of Standard Precautions is intubation, especially under emergency circumstances when infectious agents may not be suspected, but later are identified (e.g., SARS-CoV, N. meningitides). The application of Standard Precautions is described below and summarized in Table 4. Guidance on donning and removing gloves, gowns and other PPE is presented in the Figure.
Standard Precautions are also intended to protect patients by ensuring that healthcare personnel do not carry infectious agents to patients on their hands or via equipment used during patient care.  21,254,897 . The strategy proposed has been termed Respiratory Hygiene/Cough Etiquette 9,828 and is intended to be incorporated into infection control practices as a new component of Standard Precautions. The strategy is targeted at patients and accompanying family members and friends with undiagnosed transmissible respiratory infections, and applies to any person with signs of illness including cough, congestion, rhinorrhea, or increased production of respiratory secretions when entering a healthcare facility 40,41,43 . The term cough etiquette is derived from recommended source control measures for M. tuberculosis 12,126 .
The elements of Respiratory Hygiene/Cough Etiquette include 1. education of healthcare facility staff, patients, and visitors; 2. posted signs, in language(s) appropriate to the population served, with instructions to patients and accompanying family members or friends; 3. source control measures (e.g., covering the mouth/nose with a tissue when coughing and prompt disposal of used tissues, using surgical masks on the coughing person when tolerated and appropriate); 4. hand hygiene after contact with respiratory secretions; and 5. spatial separation, ideally >3 feet, of persons with respiratory infections in common waiting areas when possible.
Covering sneezes and coughs and placing masks on coughing patients are proven means of source containment that prevent infected persons from dispersing respiratory secretions into the air 107,145,898,899 . Masking may be difficult in some settings, (e.g., pediatrics, in which case, the emphasis by necessity may be on cough etiquette 900 . Physical proximity of <3 feet has been associated with an increased risk for transmission of infections via the droplet route (e.g., N. meningitidis 103 and group A streptococcus 114 and therefore supports the practice of distancing infected persons from others who are not infected. The effectiveness of good hygiene practices, especially hand hygiene, in preventing transmission of viruses and reducing the incidence of respiratory infections both within and outside  healthcare settings is summarized in several reviews 559,717,904 .
These measures should be effective in decreasing the risk of transmission of pathogens contained in large respiratory droplets (e.g., influenza virus 23 , adenovirus 111 , B. pertussis 827 and Mycoplasma pneumoniae 112 . Although fever will be present in many respiratory infections, patients with pertussis and mild upper respiratory tract infections are often afebrile. Therefore, the absence of fever does not always exclude a respiratory infection.
Patients who have asthma, allergic rhinitis, or chronic obstructive lung disease also may be coughing and sneezing. While these patients often are not infectious, cough etiquette measures are prudent.
Healthcare personnel are advised to observe Droplet Precautions (i.e., wear a mask) and hand hygiene when examining and caring for patients with signs and symptoms of a respiratory infection. Healthcare personnel who have a respiratory infection are advised to avoid direct patient contact, especially with high risk patients. If this is not possible, then a mask should be worn while providing patient care.

# III.A.1.b. Safe injection practices.
The investigation of four large outbreaks of HBV and HCV among patients in ambulatory care facilities in the United States identified a need to define and reinforce safe injection practices 453 . The four outbreaks occurred in a private medical practice, a pain clinic, an endoscopy clinic, and a hematology/oncology clinic. The primary breaches in infection control practice that contributed to these outbreaks were 1. reinsertion of used needles into a multiple-dose vial or solution container (e.g., saline bag) and 2. use of a single needle/syringe to administer intravenous medication to multiple patients.
In one of these outbreaks, preparation of medications in the same workspace where used needle/syringes were dismantled also may have been a contributing factor. These and other outbreaks of viral hepatitis could have been prevented by adherence to basic principles of aseptic technique for the preparation and administration of parenteral medications 453,454 . These include the use of a sterile, single-use, disposable needle and syringe for each injection given and prevention of contamination of injection equipment and medication. Whenever possible, use of single-dose vials is preferred over multipledose vials, especially when medications will be administered to multiple patients.
Outbreaks related to unsafe injection practices indicate that some healthcare personnel are unaware of, do not understand, or do not adhere to basic principles of infection control and aseptic technique. A survey of US healthcare workers who provide medication through injection found that 1% to 3% reused the same needle and/or syringe on multiple patients 905 . Among the deficiencies identified in recent outbreaks were a lack of oversight of personnel and failure to follow-up on reported breaches in infection control practices in ambulatory settings. Therefore, to ensure that all healthcare workers understand and adhere to recommended practices, principles of infection control and aseptic technique need to be reinforced in training programs and incorporated into institutional polices that are monitored for adherence 454 .

# III.A.1.c. Infection Control Practices for Special Lumbar Puncture Procedures.
In 2004, CDC investigated eight cases of post-myelography meningitis that either were reported to CDC or identified through a survey of the Emerging Infections Network of the Infectious Disease Society of America. Blood and/or cerebrospinal fluid of all eight cases yielded streptococcal species consistent with oropharyngeal flora and there were changes in the CSF indices and clinical status indicative of bacterial meningitis. Equipment and products used during these procedures (e.g., contrast media) were excluded as probable sources of contamination. Procedural details available for seven cases determined that antiseptic skin preparations and sterile gloves had been used. However, none of the clinicians wore a face mask, giving rise to the speculation that droplet transmission of oralpharyngeal flora was the most likely explanation for these infections. Bacterial meningitis following myelogram and other spinal procedures (e.g., lumbar puncture, spinal and epidural anesthesia, intrathecal chemotherapy) has been reported previously  .
As a result, the question of whether face masks should be worn to prevent droplet spread of oral flora during spinal procedures (e.g., myelogram, lumbar puncture, spinal anesthesia) has been debated 916,917 . Face masks are effective in limiting the dispersal of oropharyngeal droplets 918 and are recommended for the placement of central venous catheters 919 . In October 2005, the Healthcare Infection Control Practices Advisory Committee (HICPAC) reviewed the evidence and concluded that there is sufficient experience to warrant the additional protection of a face mask for the individual placing a catheter or injecting material into the spinal or epidural space.

# III.B. Transmission-Based Precautions
There are three categories of Transmission-Based Precautions: Contact Precautions, Droplet Precautions, and Airborne Precautions. Transmission-Based Precautions are used when the route(s) of transmission is (are) not completely interrupted using Standard Precautions alone. For some diseases that have multiple routes of transmission (e.g., SARS), more than one Transmission-Based Precautions category may be used. When used either singly or in combination, they are always used in addition to Standard Precautions. See Appendix A for recommended precautions for specific infections. When Transmission-Based Precautions are indicated, efforts must be made to counteract possible adverse effects on patients (i.e., anxiety, depression and other mood disturbances  , perceptions of stigma 923 , reduced contact with clinical staff  , and increases in preventable adverse events 565 in order to improve acceptance by the patients and adherence by HCWs.

# III.B.1. Contact precautions.
Contact Precautions are intended to prevent transmission of infectious agents, including epidemiologically important microorganisms, which are spread by direct or indirect contact with the patient or the patient's environment as described in I.B.  12,13 . Some states require the availability of such rooms in hospitals, emergency departments, and nursing homes that care for patients with M. tuberculosis. A respiratory protection program that includes education about use of respirators, fit-testing, and user seal checks is required in any facility with AIIRs. In settings where Airborne Precautions cannot be implemented due to limited engineering resources (e.g., physician offices), masking the patient, placing the patient in a private room (e.g., office examination room) with the door closed, and providing N95 or higher level respirators or masks if respirators are not available for healthcare personnel will reduce the likelihood of airborne transmission until the patient is either transferred to a facility with an AIIR or returned to the home environment, as deemed medically appropriate. Healthcare personnel caring for patients on Airborne Precautions wear a mask or respirator, depending on the disease-specific recommendations (Respiratory Protection II.E.4, Table 2, and Appendix A), that is donned prior to room entry. Whenever possible, non-immune HCWs should not care for patients with vaccine-preventable airborne diseases (e.g., measles, chickenpox, and smallpox).

# III.C. Syndromic and Empiric Applications of Transmission-Based Precautions
Diagnosis of many infections requires laboratory confirmation. Since laboratory tests, especially those that depend on culture techniques, often require two or more days for completion, Transmission-Based Precautions must be implemented while test results are pending based on the clinical presentation and likely pathogens. Use of appropriate Transmission-Based Precautions at the time a patient develops symptoms or signs of transmissible infection, or arrives at a healthcare facility for care, reduces transmission opportunities. While it is not possible to identify prospectively all patients needing Transmission-Based Precautions, certain clinical syndromes and conditions carry a sufficiently high risk to warrant their use empirically while confirmatory tests are pending (Table 2). Infection control professionals are encouraged to modify or adapt this table according to local conditions.

# III.D. Discontinuation of Transmission-Based Precautions Transmission-Based
Precautions remain in effect for limited periods of time (i.e., while the risk for transmission of the infectious agent persists or for the duration of the illness (Appendix A). For most infectious diseases, this duration reflects known patterns of persistence and shedding of infectious agents associated with the natural history of the infectious process and its treatment. For some diseases (e.g., pharyngeal or cutaneous diphtheria, RSV), Transmission-Based Precautions remain in effect until culture or antigen-detection test results document eradication of the pathogen and, for RSV, symptomatic disease is resolved. For other diseases, (e.g., M. tuberculosis) state laws and regulations, and healthcare facility policies, may dictate the duration of precautions 12 ). In immunocompromised patients, viral shedding can persist for prolonged periods of time (many weeks to months) and transmission to others may occur during that time; therefore, the duration of contact and/or droplet precautions may be prolonged for many weeks 500, .
The duration of Contact Precautions for patients who are colonized or infected with MDROs remains undefined. MRSA is the only MDRO for which effective decolonization regimens are available 867 . However, carriers of MRSA who have negative nasal cultures after a course of systemic or topical therapy may resume shedding MRSA in the weeks that follow therapy 934,935 . Although early guidelines for VRE suggested discontinuation of Contact Precautions after three stool cultures obtained at weekly intervals proved negative 740 , subsequent experiences have indicated that such screening may fail to detect colonization that can persist for >1 year 27, . Likewise, available data indicate that colonization with VRE, MRSA 939 , and possibly MDR-GNB, can persist for many months, especially in the presence of severe underlying disease, invasive devices, and recurrent courses of antimicrobial agents.
It may be prudent to assume that MDRO carriers are colonized permanently and manage them accordingly. Alternatively, an interval free of hospitalizations, antimicrobial therapy, and invasive devices (e.g., 6 or 12 months) before reculturing patients to document clearance of carriage may be used. Determination of the best strategy awaits the results of additional studies. See the 2006 HICPAC/CDC MDRO guideline 927 for discussion of possible criteria to discontinue Contact Precautions for patients colonized or infected with MDROs.

# III.E. Application of Transmission-Based Precautions in Ambulatory and Home
Care Settings Although Transmission-Based Precautions generally apply in all healthcare settings, exceptions exist. For example, in home care, AIIRs are not available. Furthermore, family members already exposed to diseases such as varicella and tuberculosis would not use masks or respiratory protection, but visiting HCWs would need to use such protection. Similarly, management of patients colonized or infected with MDROs may necessitate Contact Precautions in acute care hospitals and in some LTCFs when there is continued transmission, but the risk of transmission in ambulatory care and home care, has not been defined. Consistent use of Standard Precautions may suffice in these settings, but more information is needed.

# III.F. Protective EnvironmentA
Protective Environment is designed for allogeneic HSCT patients to minimize fungal spore counts in the air and reduce the risk of invasive environmental fungal infections (see Table 5 for specifications) 11, . The need for such controls has been demonstrated in studies of aspergillus outbreaks associated with construction 11,14,15,157,158 . As defined by the American Insitute of Architecture 13 and presented in detail in the Guideline for Environmental Infection Control 2003 11,861 , air quality for HSCT patients is improved through a combination of environmental controls that include 1. HEPA filtration of incoming air;
2. directed room air flow; 3. positive room air pressure relative to the corridor; 4. well-sealed rooms (including sealed walls, floors, ceilings, windows, electrical outlets) to prevent flow of air from the outside; 5. ventilation to provide >12 air changes per hour; 6. strategies to minimize dust (e.g., scrubbable surfaces rather than upholstery 940 and carpet 941 , and routinely cleaning crevices and sprinkler heads); and 7. prohibiting dried and fresh flowers and potted plants in the rooms of HSCT patients.
The latter is based on molecular typing studies that have found indistinguishable strains of Aspergillus terreus in patients with hematologic malignancies and in potted plants in the vicinity of the patients  . The desired quality of air may be achieved without incurring the inconvenience or expense of laminar airflow 15,157 . To prevent inhalation of fungal spores during periods when construction, renovation, or other dust-generating activities that may be ongoing in and around the health-care facility, it has been advised that severely immunocompromised patients wear a high-efficiency respiratory-protection device (e.g., an N95 respirator) when they leave the Protective Environment 11,14,945 ). The use of masks or respirators by HSCT patients when they are outside of the Protective Environment for prevention of environmental fungal infections in the absence of construction has not been evaluated. A Protective Environment does not include the use of barrier precautions beyond those indicated for Standard and Transmission-Based Precautions. No published reports support the benefit of placing solid organ transplants or other immunocompromised patients in a Protective Environment.

# Part IV: Recommendations
These recommendations are designed to prevent transmission of infectious agents among patients and healthcare personnel in all settings where healthcare is delivered. As in other CDC/HICPAC guidelines, each recommendation is categorized on the basis of existing scientific data, theoretical rationale, applicability, and when possible, economic impact. The CDC/HICPAC system for categorizing recommendations is as follows:
Category IA Strongly recommended for implementation and strongly supported by welldesigned experimental, clinical, or epidemiologic studies.
Category IB Strongly recommended for implementation and supported by some experimental, clinical, or epidemiologic studies and a strong theoretical rationale.
Category IC Required for implementation, as mandated by federal and/or state regulation or standard.
Category II Suggested for implementation and supported by suggestive clinical or epidemiologic studies or a theoretical rationale.
No recommendation; unresolved issue. Practices for which insufficient evidence or no consensus regarding efficacy exists.

# I. Administrative Responsibilities
Healthcare organization administrators should ensure the implementation of recommendations in this section.

# I.A.
Incorporate preventing transmission of infectious agents into the objectives of the organization's patient and occupational safety programs 543-546, 561, 620, 626, 946 566 247 687 . Category IB III.E. Review periodically information on community or regional trends in the incidence and prevalence of epidemiologically-important organisms (e.g., influenza, RSV, pertussis, invasive group A streptococcal disease, MRSA, VRE) (including in other healthcare facilities) that may impact transmission of organisms within the facility 398, 687, 972, 973 974 . Category II

# IV. Standard Precautions
Assume that every person is potentially infected or colonized with an organism that could be transmitted in the healthcare setting and apply the following infection control practices during the delivery of health care.    956 IV.E.1. Establish policies and procedures for containing, transporting, and handling patient-care equipment and instruments/devices that may be contaminated with blood or body fluids 18,739,975 . Category IB/IC

# IV.A. Hand Hygiene
IV.E.2. Remove organic material from critical and semi-critical instrument/devices, using recommended cleaning agents before high level disinfection and sterilization to enable effective disinfection and sterilization processes 836 991, 992 . Category IA IV.E.3. Wear PPE (e.g., gloves, gown), according to the level of anticipated contamination, when handling patient-care equipment and instruments/devices that is visibly soiled or may have been in contact with blood or body fluids 18,739,975 . Category IB/IC

# IV.F. Care of the Environment 11
Edit : An - indicates recommendations that were renumbered for clarity. The renumbering does not constitute change to the intent of the recommendations.
IV.F.1. Establish policies and procedures for routine and targeted cleaning of environmental surfaces as indicated by the level of patient contact and degree of soiling 11 . Category II IV.F.2. Clean and disinfect surfaces that are likely to be contaminated with pathogens, including those that are in close proximity to the patient (e.g., bed rails, over bed tables) and frequently-touched surfaces in the patient care environment (e.g., door knobs, surfaces in and surrounding toilets in patients' rooms) on a more frequent schedule compared to that for other surfaces (e.g., horizontal surfaces in waiting rooms) 11 73, 740, 746, 993, 994 72, 800, 835 995 . Category IB IV.F.3. Use EPA-registered disinfectants that have microbiocidal (i.e., killing) activity against the pathogens most likely to contaminate the patient-care environment. Use in accordance with manufacturer's instructions 842-844, 956, 996 . Category IB/IC IV.F.3.a. Review the efficacy of in-use disinfectants when evidence of continuing transmission of an infectious agent (e.g., rotavirus, C. difficile, norovirus) may indicate resistance to the in-use product and change to a more effective disinfectant as indicated 275,842,847 .

# Category II
Edit : An - indicates recommendations that were renumbered for clarity. The renumbering does not constitute change to the intent of the recommendations.
IV.F.4. In facilities that provide health care to pediatric patients or have waiting areas with child play toys (e.g., obstetric/gynecology offices and clinics), establish policies and procedures for cleaning and disinfecting toys at regular intervals 379 80 . Category IB IV.F.4.a. - Use the following principles in developing this policy and procedures: Category II
- Select play toys that can be easily cleaned and disinfected - Do not permit use of stuffed furry toys if they will be shared - Clean and disinfect large stationary toys (e.g., climbing quipment) at least weekly and whenever visibly soiled
- If toys are likely to be mouthed, rinse with water after disinfection; alternatively wash in a dishwasher
- When a toy requires cleaning and disinfection, do so immediately or store in a designated labeled container separate from toys that are clean and ready for use IV.F.5. Include multi-use electronic equipment in policies and procedures for preventing contamination and for cleaning and disinfection, especially those items that are used by patients, those used during delivery of patient care, and mobile devices that are moved in and out of patient rooms frequently (e.g., daily) 850 851, 852, 997 . Category IB IV.F.5.a. No recommendation for use of removable protective covers or washable keyboards. Unresolved issue

# IV.G. Textiles and Laundry
IV.G.1. Handle used textiles and fabrics with minimum agitation to avoid contamination of air, surfaces and persons 739,998,999 . Category IB/IC IV.G.2. If laundry chutes are used, ensure that they are properly designed, maintained, and used in a manner to minimize dispersion of aerosols from contaminated laundry 11,13,1000,1001 . Category IB/IC

# IV.H. Safe Injection Practices
The following recommendations apply to the use of needles, cannulas that replace needles, and, where applicable, intravenous delivery systems 454 IV.H.1. Use aseptic technique to avoid contamination of sterile injection equipment 1002, 1003 . Category IA IV.H.2. Do not administer medications from a syringe to multiple patients, even if the needle or cannula on the syringe is changed. Needles, cannulae and syringes are sterile, single-use items; they should not be reused for another patient nor to access a medication or solution that might be used for a subsequent patient 453,919,1004,1005 . Category IA IV.H.3. Use fluid infusion and administration sets (i.e., intravenous bags, tubing and connectors) for one patient only and dispose appropriately after use. Consider a syringe or needle/cannula contaminated once it has been used to enter or connect to a patient's intravenous infusion bag or administration set 453 . Category IB IV.H.4. Use single-dose vials for parenteral medications whenever possible 453 .

# Category IA
IV.H.5. Do not administer medications from single-dose vials or ampules to multiple patients or combine leftover contents for later use 369 453, 1005 . Category IA IV.H.6. If multidose vials must be used, both the needle or cannula and syringe used to access the multidose vial must be sterile 453,1002 . Category IA IV.H.7. Do not keep multidose vials in the immediate patient treatment area and store in accordance with the manufacturer's recommendations; discard if sterility is compromised or questionable 453,1003 . Category IA IV.H.8. Do not use bags or bottles of intravenous solution as a common source of supply for multiple patients 453,1006 . Category IB IV.I. Infection control practices for special lumbar puncture procedures Wear a surgical mask when placing a catheter or injecting material into the spinal canal or subdural space (i.e., during myelograms, lumbar puncture and spinal or epidural anesthesia). 906

# V.C. Droplet Precautions
Use Droplet Precautions as recommended in Appendix A for patients known or suspected to be infected with pathogens transmitted by respiratory droplets (i.e., large-particle droplets >5 in size) that are generated by a patient who is coughing, sneezing or talking 14, 23, Steinberg, 1969  to exhaust air from an AIIR directly to the outside, the air may be returned to the air-handling system or adjacent spaces if all air is directed through HEPA filters.
V.D.2.a.iii. Whenever an AIIR is in use for a patient on Airborne Precautions, monitor air pressure daily with visual indicators (e.g., smoke tubes, flutter strips), regardless of the presence of differential pressure sensing devices (e.g., manometers) 11,12,1023,1024 .
V.D.2.a.iv. Keep the AIIR door closed when not required for entry and exit. V.D.2.b. When an AIIR is not available, transfer the patient to a facility that has an available AIIR 12 . Category II V.D.2.c. In the event of an outbreak or exposure involving large numbers of patients who require Airborne Precautions:  Consult infection control professionals before patient placement to determine the safety of alternative room that do not meet engineering requirements for an AIIR.  Place together (cohort) patients who are presumed to have the same infection( based on clinical presentation and diagnosis when known) in areas of the facility that are away from other patients, especially patients who are at increased risk for infection (e.g., immunocompromised patients).  Use temporary portable solutions (e.g., exhaust fan) to create a negative pressure environment in the converted area of the facility. Discharge air directly to the outside,away from people and air intakes, or direct all the air through HEPA filters before it is introduced to other air spaces 12 Category II V.D.2.d. In ambulatory settings: V.D.2.d.i. Develop systems (e.g., triage, signage) to identify patients with known or suspected infections that require Airborne Precautions upon entry into ambulatory settings 9,12,34,127,134 . Category IA V.D.2.d.ii. Place the patient in an AIIR as soon as possible. If an AIIR is not available, place a surgical mask on the patient and place him/her in an examination room.
Once the patient leaves, the room should remain vacant for the appropriate time, generally one hour, to allow for a full exchange of air 11,12,122 . Category IB/IC V.D.2.d.iii. Instruct patients with a known or suspected airborne infection to wear a surgical mask and observe Respiratory Hygiene/Cough Etiquette. Once in an AIIR, the mask may be removed; the mask should remain on if the patient is not in an AIIR 12,107,145,899 . Category IB/IC V.D.3. Personnel restrictions Restrict susceptible healthcare personnel from entering the rooms of patients known or suspected to have measles (rubeola), varicella (chickenpox), disseminated zoster, or smallpox if other immune healthcare personnel are available 17,775 . Category IB V.D.4.a. Wear a fit-tested NIOSH-approved N95 or higher level respirator for respiratory protection when entering the room or home of a patient when the following diseases are suspected or confirmed:  - V.D.4.a.i. Infectious pulmonary or laryngeal tuberculosis or when infectious tuberculosis skin lesions are present and procedures that would aerosolize viable organisms (e.g., irrigation, incision and drainage, whirlpool treatments) are performed 12,1025,1026 . Category IB  - V.D.4.a.ii. Smallpox (vaccinated and unvaccinated).
Respiratory protection is recommended for all healthcare personnel, including those with a documented "take" after smallpox vaccination due to the risk of a genetically engineered virus against which the vaccine may not provide protection, or of exposure to a very large viral load (e.g., from high-risk aerosol-generating procedures, immunocompromised patients, hemorrhagic or flat smallpox 108,129 . Category II V.D.4.b.  Suspected measles, chickenpox or disseminated zoster. No recommendation is made regarding the use of PPE by healthcare personnel who are presumed to be immune to measles (rubeola) or varicella-zoster based on history of disease, vaccine, or serologic testing when caring for an individual with known or suspected measles, chickenpox or disseminated zoster, due to difficulties in establishing definite immunity 1027,1028 . Unresolved issue V.D.4.c.  Suspected measles, chickenpox or disseminated zoster. No recommendation is made regarding the type of personal protective equipment (i.e., surgical mask or respiratory protection with a N95 or higher respirator) to be worn by susceptible healthcare personnel who must have contact with patients with known or suspected measles, chickenpox or disseminated herpes zoster. Unresolved issue V.D.  13 . Category IB VI.C.2. Lower dust levels by using smooth, nonporous surfaces and finishes that can be scrubbed, rather than textured material (e.g., upholstery). Wet dust horizontal surfaces whenever dust detected and routinely clean crevices and sprinkler heads where dust may accumulate 940,941 . Category II VI.C.3. Avoid carpeting in hallways and patient rooms in areas 941 . Category IB VI.C.4. Prohibit dried and fresh flowers and potted plants  . Category II VI.D. Minimize the length of time that patients who require a Protective Environment are outside their rooms for diagnostic procedures and other activities 11,158,945 .

# Category IB
VI.E. During periods of construction, to prevent inhalation of respirable particles that could contain infectious spores, provide respiratory protection (e.g., N95 respirator) to patients who are medically fit to tolerate a respirator when they are required to leave the Protective Environment 945 158 13 . Category IB VI.F.4.b. Use an anteroom to further support the appropriate air-balance relative to the corridor and the Protective Environment; provide independent exhaust of contaminated air to the outside or place a HEPA filter in the exhaust duct if the return air must be recirculated 13,1041 . Category IB VI.F.4.c. If an anteroom is not available, place the patient in an AIIR and use portable, industrial-grade HEPA filters in the room to enhance filtration of spores 1042 . Category II Preamble The mode(s) and risk of transmission for each specific disease agent included in Appendix A were reviewed. Principle sources consulted for the development of disease-specific recommendations for Appendix A included infectious disease manuals and textbooks . The published literature was searched for evidence of person-to-person transmission in healthcare and non-healthcare settings with a focus on reported outbreaks that would assist in developing recommendations for all settings where healthcare is delivered. Criteria used to assign Transmission-Based Precautions categories follow:
- A Transmission-Based Precautions category was assigned if there was strong evidence for person-to-person transmission via droplet, contact, or airborne routes in healthcare or nonhealthcare settings and/or if patient factors (e.g., diapered infants, diarrhea, draining wounds) increased the risk of transmission - Transmission-Based Precautions category assignments reflect the predominant mode(s) of transmission - If there was no evidence for person-to-person transmission by droplet, contact or airborne routes, Standard Precautions were assigned - If there was a low risk for person-to-person transmission and no evidence of healthcareassociated transmission, Standard Precautions were assigned - Standard Precautions were assigned for bloodborne pathogens (e.g., hepatitis B and C viruses, human immunodeficiency virus) as per CDC recommendations for Universal Precautions issued in 1988 . Subsequent experience has confirmed the efficacy of Standard Precautions to prevent exposure to infected blood and body fluid .
Additional information relevant to use of precautions was added in the comments column to assist the caregiver in decision-making. Citations were added as needed to support a change in or provide additional evidence for recommendations for a specific disease and for new infectious agents (e.g., SARS-CoV, avian influenza) that have been added to Appendix A. The reader may refer to more detailed discussion concerning modes of transmission and emerging pathogens in the background text and for MDRO control in Appendix B (Management of Multidrug-Resistant Organisms in Healthcare Settings (/)).  ; ensure consistent environmental cleaning and disinfection with focus on restrooms even when apparently unsoiled ). Hypochlorite solutions may be required when there is continued transmission . Alcohol is less active, but there is no evidence that alcohol antiseptic handrubs are not effective for hand decontamination . Cohorting of affected patients to separate airspaces and toilet facilities may help interrupt transmission during outbreaks. Gastroenteritis Rotavirus

# Type and Duration of Precautions Recommended for Selected Infections and Conditions 1 Infection/Condition

# Type of Precaution

# Contact + Standard

# Duration of illness
Ensure consistent environmental cleaning and disinfection and frequent removal of soiled diapers. Prolonged shedding may occur in both immunocompetent and immunocompromised children and the elderly .     Gastrointestinal Tract: Ingestion of toxin-containing food, Respiratory Tract: Inhalation of toxin containing aerosol cause disease. Comment: Toxin ingested or potentially delivered by aerosol in bioterrorist incidents. LD50 (lethal dose for 50% of experimental animals) for type A is 0.001 g/ml/kg. Incubation Period 1-5 days.

# Infection/Condition

# Type of Precaution

# Clinical Features
Ptosis, generalized weakness, dizziness, dry mouth and throat, blurred vision, diplopia, dysarthria, dysphonia, and dysphagia followed by symmetrical descending paralysis and respiratory failure.

# Diagnosis
Clinical diagnosis; identification of toxin in stool, serology unless toxin-containing material available for toxin neutralization bioassays.

# Characteristics Infection Control Considerations Infectivity
Not transmitted from person to person. Exposure to toxin necessary for disease.

# Recommended Precautions
Standard Precautions.

# Ebola Hemorrhagic Fever
Ebola Virus Disease for Healthcare Workers: Updated recommendations for healthcare workers can be found at Ebola: U.S. Healthcare Workers and Settings (/).

# Table 3C. Ebola Hemorrhagic Fever Characteristics Infection Control Considerations Site(s) of Infection; Transmission Mode
As a rule infection develops after exposure of mucous membranes or respiratory tract, or through broken skin or percutaneous injury. Incubation Period 2-19 days, usually 5-10 days

# Clinical Features
Febrile illnesses with malaise, myalgias, headache, vomiting and diarrhea that are rapidly complicated by hypotension, shock, and hemorrhagic features. Massive hemorrhage in < 50% pts.

# Diagnosis
Etiologic diagnosis can be made using respiratory tract-polymerase chain reaction, serologic detection of antibody and antigen, pathologic assessment with immunohistochemistry and viral culture with EM confirmation of morphology,

# Infectivity
Person-to-person transmission primarily occurs through unprotected contact with blood and body fluids; percutaneous injuries (e.g., needlestick) associated with a high rate of transmission; transmission in healthcare settings has been reported but is prevented by use of barrier precautions.

# Recommended Precautions
Hemorrhagic fever specific barrier precautions: If disease is believed to be related to intentional release of a bioweapon, epidemiology of transmission is unpredictable pending observation of disease transmission. Until the nature of the pathogen is understood and its transmission pattern confirmed, Standard, Contact and Airborne Precautions should be used. Once the pathogen is characterized, if the epidemiology of transmission is consistent with natural disease, Droplet Precautions can be substituted for Airborne Precautions. Emphasize: 1. use of sharps safety devices and safe work practices, 2. hand hygiene; 3. barrier protection against blood and body fluids upon entry into room (single gloves and fluid-resistant or impermeable gown, face/eye protection with masks, goggles or face shields); and 4. appropriate waste handling. Use N95 or higher respirators when performing aerosol-generating procedures. In settings where AIIRs are unavailable or the large numbers of patients cannot be accommodated by existing AIIRs, observe Droplet Precautions (plus Standard Precautions and Contact Precautions) and segregate patients from those not suspected of VHF infection. Limit blooddraws to those essential to care. See text for discussion and Appendix A for recommendations for naturally occurring VHFs.

# Plague
Pneumonic plague is not as contagious as is often thought. Historical accounts and contemporary evidence indicate that persons with plague usually transmit the infection only when the disease is in the end stage. These persons cough copious amounts of bloody sputum that contains many plague bacteria. Patients in the early stage of primary pneumonic plague (approximately the first 20-24 h) apparently pose little risk . Antibiotic medication rapidly clears the sputum of plague bacilli, so that a patient generally is not infective within hours after initiation of effective antibiotic treatment . This means that in modern times many patients will never reach a stage where they pose a significant risk to others. Even in the end stage of disease, transmission only occurs after close contact. Simple protective measures, such as wearing masks, good hygiene, and avoiding close contact, have been effective to interrupt transmission during many pneumonic plague outbreaks . In the United States, the last known cases of person to person transmission of pneumonic plague occurred in 1925 .

# Characteristics Infection Control Considerations Clinical Features
Fever, malaise, backache, headache, and often vomiting for 2-3 days; then generalized papular or maculopapular rash (more on face and extremities), which becomes vesicular (on day 4 or 5) and then pustular; lesions all in same stage.

# Diagnosis
Electron microscopy of vesicular fluid or culture of vesicular fluid by WHO approved laboratory (CDC); detection by polymerase chain reaction available only in select LRN labs, CDC and USAMRID Infectivity Secondary attack rates up to 50% in unvaccinated persons; infected persons may transmit disease from time rash appears until all lesions have crusted over (about 3 weeks); greatest infectivity during first 10 days of rash.

# Recommended Precautions
Combined use of Standard, Contact, and Airborne Precautions until all scabs have separated (3-4 weeks). Transmission by the airborne route is a rare event; Airborne Precautions is recommended when possible, but in the event of mass exposures, barrier precautions and containment within a designated area are most important. 204,212 Only immune HCWs to care for pts; post-exposure vaccine within 4 days. Vaccinia: HCWs cover vaccination site with gauze and semi-permeable dressing until scab separates (21 days). Observe hand hygiene. Adverse events with virus-containing lesions: Standard plus Contact Precautions until all lesions crusted. Vaccinia adverse events with lesions containing infectious virus include inadvertent autoinoculation, ocular lesions (blepharitis, conjunctivitis), generalized vaccinia, progressive vaccinia, eczema vaccinatum; bacterial superinfection also requires addition of contact precautions if exudates cannot be contained. 216,217

# Table 3F. Tularemia Characteristics Infection Control Considerations Site(s) of Infection; Transmission Mode
Respiratory Tract: Inhalation of aerosolized bacteria. Gastrointestinal Tract: Ingestion of food or drink contaminated with aerosolized bacteria. Comment: Pneumonic or typhoidal disease likely to occur after bioterrorist event using aerosol delivery. Infective dose 10-50 bacteria Incubation Period 2 to 10 days, usually 3 to 5 days

# Clinical Features
Pneumonic: malaise, cough, sputum production, dyspnea; Typhoidal: fever, prostration, weight loss and frequently an associated pneumonia.

# Diagnosis
Diagnosis usually made with serology on acute and convalescent serum specimens; bacterium can be detected by polymerase chain reaction (LRN) or isolated from blood and other body fluids on cysteine-enriched media or mouse inoculation.

# Infectivity
Person-to-person spread is rare. Laboratory workers who encounter/handle cultures of this organism are at high risk for disease if exposed.   (e.g., flutter strips, smoke tubes) or a hand held pressure gauge - Self-closing door on all room exits - Maintain back-up ventilation equipment (e.g., portable units for fans or filters) for emergency provision of ventilation requirements for PE areas and take immediate steps to restore the fixed ventilation system - For patients who require both a PE and Airborne Infection Isolation, use an anteroom to ensure proper air balance relationships and provide independent exhaust of contaminated air to the outside or place a HEPA filter in the exhaust duct. If an anteroom is not available, place patient in an AIIR and use portable ventilation units, industrial-grade HEPA filters to enhance filtration of spores.

# Recommended Precautions
Standard Precautions

# IV. Surfaces
- Cohorting. In the context of this guideline, this term applies to the practice of grouping patients infected or colonized with the same infectious agent together to confine their care to one area and prevent contact with susceptible patients (cohorting patients). During outbreaks, healthcare personnel may be assigned to a cohort of patients to further limit opportunities for transmission (cohorting staff).
Colonization. Proliferation of microorganisms on or within body sites without detectable host immune response, cellular damage, or clinical expression. The presence of a microorganism within a host may occur with varying duration, but may become a source of potential transmission. In many instances, colonization and carriage are synonymous.
Droplet nuclei. Microscopic particles < 5 m in size that are the residue of evaporated droplets and are produced when a person coughs, sneezes, shouts, or sings. These particles can remain suspended in the air for prolonged periods of time and can be carried on normal air currents in a room or beyond, to adjacent spaces or areas receiving exhaust air.

# Hand hygiene.
A general term that applies to any one of the following: 1. handwashing with plain (nonantimicrobial) soap and water); 2. antiseptic handwash (soap containing antiseptic agents and water); 3. antiseptic handrub (waterless antiseptic product, most often alcohol-based, rubbed on all surfaces of hands); or 4. surgical hand antisepsis (antiseptic handwash or antiseptic handrub performed preoperatively by surgical personnel to eliminate transient hand flora and reduce resident hand flora) 559 .

# Healthcare-associated infection (HAI).
An infection that develops in a patient who is cared for in any setting where healthcare is delivered (e.g., acute care hospital, chronic care facility, ambulatory clinic, dialysis center, surgicenter, home) and is related to receiving health care (i.e., was not incubating or present at the time healthcare was provided). In ambulatory and home settings, HAI would apply to any infection that is associated with a medical or surgical intervention. Since the geographic location of infection acquisition is often uncertain, the preferred term is considered to be healthcare-associated rather than healthcare-acquired.
Healthcare epidemiologist. A person whose primary training is medical (M.D., D.O.) and/or masters or doctorate-level epidemiology who has received advanced training in healthcare epidemiology. Typically these professionals direct or provide consultation to an infection control program in a hospital, long term care facility (LTCF), or healthcare delivery system (also see infection control professional).

# Healthcare personnel, healthcare worker (HCW).
All paid and unpaid persons who work in a healthcare setting (e.g., any person who has professional or technical training in a healthcare-related field and provides patient care in a healthcare setting or any person who provides services that support the delivery of healthcare such as dietary, housekeeping, engineering, maintenance personnel).

# Hematopoietic stem cell transplantation (HSCT).
Any transplantation of bloodor bone marrow-derived hematopoietic stem cells, regardless of donor type (e.g., allogeneic or autologous) or cell source (e.g., bone marrow, peripheral blood, or placental/umbilical cord blood); associated with periods of severe immunosuppression that vary with the source of the cells, the intensity of chemotherapy required, and the presence of graft versus host disease (MMWR 2000; 49: RR-10).
High-efficiency particulate air (HEPA) filter. An air filter that removes >99.97% of particles  0.3m (the most penetrating particle size) at a specified flow rate of air. HEPA filters may be integrated into the central air handling systems, installed at the point of use above the ceiling of a room, or used as portable units (MMWR 2003; 52: RR-10).
Home care. A wide-range of medical, nursing, rehabilitation, hospice and social services delivered to patients in their place of residence (e.g., private residence, senior living center, assisted living facility). Home health-care services include care provided by home health aides and skilled nurses, respiratory therapists, dieticians, physicians, chaplains, and volunteers; provision of durable medical equipment; home infusion therapy; and physical, speech, and occupational therapy.

# Immunocompromised patients.
Those patients whose immune mechanisms are deficient because of congenital or acquired immunologic disorders (e.g., human immunodeficiency virus  infection, congenital immune deficiency syndromes), chronic diseases such as diabetes mellitus, cancer, emphysema, or cardiac failure, ICU care, malnutrition, and immunosuppressive therapy of another disease process ). The type of infections for which an immunocompromised patient has increased susceptibility is determined by the severity of immunosuppression and the specific component(s) of the immune system that is affected. Patients undergoing allogeneic HSCT and those with chronic graft versus host disease are considered the most vulnerable to HAIs. Immunocompromised states also make it more difficult to diagnose certain infections (e.g., tuberculosis) and are associated with more severe clinical disease states than persons with the same infection and a normal immune system.
Infection. The transmission of microorganisms into a host after evading or overcoming defense mechanisms, resulting in the organism's proliferation and invasion within host tissue(s). Host responses to infection may include clinical symptoms or may be subclinical, with manifestations of disease mediated by direct organisms pathogenesis and/or a function of cell-mediated or antibody responses that result in the destruction of host tissues.

# Infection control and prevention professional (ICP).
A person whose primary training is in either nursing, medical technology, microbiology, or epidemiology and who has acquired specialized training in infection control. Responsibilities may include collection, analysis, and feedback of infection data and trends to healthcare providers; consultation on infection risk assessment, prevention and control strategies; performance of education and training activities; implementation of evidence-based infection control practices or those mandated by regulatory and licensing agencies; application of epidemiologic principles to improve patient outcomes; participation in planning renovation and construction projects (e.g., to ensure appropriate containment of construction dust); evaluation of new products or procedures on patient outcomes; oversight of employee health services related to infection prevention; implementation of preparedness plans; communication within the healthcare setting, with local and state health departments, and with the community at large concerning infection control issues; and participation in research. Certification in infection control (CIC) is available through the Certification Board of Infection Control and Epidemiology.

# Infection control and prevention program.
A multidisciplinary program that includes a group of activities to ensure that recommended practices for the prevention of healthcare-associated infections are implemented and followed by HCWs, making the healthcare setting safe from infection for patients and healthcare personnel. The Joint Commission on Accreditation of Healthcare Organizations (JCAHO) requires the following five components of an infection control program for accreditation: 1. surveillance: monitoring patients and healthcare personnel for acquisition of infection and/or colonization; 2. investigation: identification and analysis of infection problems or undesirable trends; 3. prevention: implementation of measures to prevent transmission of infectious agents and to reduce risks for device-and procedure-related infections; 4) control: evaluation and management of outbreaks; and 4. reporting: provision of information to external agencies as required by state and federal law and regulation (The Joint Commission (/) ).
The infection control program staff has the ultimate authority to determine infection control policies for a healthcare organization with the approval of the organization's governing body.
Long-term care facilities (LTCFs). An array of residential and outpatient facilities designed to meet the bio-psychosocial needs of persons with sustained self-care deficits. These include skilled nursing facilities, chronic disease hospitals, nursing homes, foster and group homes, institutions for the developmentally disabled, residential care facilities, assisted living facilities, retirement homes, adult day health care facilities, rehabilitation centers, and long-term psychiatric hospitals.

# Mask.
A term that applies collectively to items used to cover the nose and mouth and includes both procedure masks and surgical masks (

# Multidrug-resistant organisms (MDROs).
In general, bacteria (excluding M. tuberculosis) that are resistant to one or more classes of antimicrobial agents and usually are resistant to all but one or two commercially available antimicrobial agents (e.g., MRSA, VRE, extended spectrum beta-lactamase -producing or intrinsically resistant gram-negative bacilli) 176 .

# Nosocomial infection. Derived from two
Greek words "nosos" (disease) and "komeion" (to take care of). Refers to any infection that develops during or as a result of an admission to an acute care facility (hospital) and was not incubating at the time of admission.

# Personal protective equipment (PPE).
A variety of barriers used alone or in combination to protect mucous membranes, skin, and clothing from contact with infectious agents. PPE includes gloves, masks, respirators, goggles, face shields, and gowns.

# Procedure Mask.
A covering for the nose and mouth that is intended for use in general patient care situations. These masks generally attach to the face with ear loops rather than ties or elastic. Unlike surgical masks, procedure masks are not regulated by the Food and Drug Administration.
Protective Environment. A specialized patient-care area, usually in a hospital, with a positive air flow relative to the corridor (i.e., air flows from the room to the outside adjacent space). The combination of high-efficiency particulate air (HEPA) filtration, high numbers (12) of air changes per hour (ACH), and minimal leakage of air into the room creates an environment that can safely accommodate patients with a severely compromised immune system (e.g., those who have received allogeneic hemopoietic stem-cell transplant ) and decrease the risk of exposure to spores produced by environmental fungi. Other components include use of 2. using tissues to contain respiratory secretions with prompt disposal into a notouch receptacle, 3. offering a surgical mask to persons who are coughing to decrease contamination of the surrounding environment, and 4. turning the head away from others and maintaining spatial separation, ideally >3 feet, when coughing.
These measures are targeted to all patients with symptoms of respiratory infection and their accompanying family members or friends beginning at the point of initial encounter with a healthcare setting (e.g., reception/triage in emergency departments, ambulatory clinics, healthcare provider offices) 126 620 .
Source Control. The process of containing an infectious agent either at the portal of exit from the body or within a confined space. The term is applied most frequently to containment of infectious agents transmitted by the respiratory route but could apply to other routes of transmission, (e.g., a draining wound, vesicular or bullous skin lesions). Respiratory Hygiene/Cough Etiquette that encourages individuals to "cover your cough" and/or wear a mask is a source control measure. The use of enclosing devices for local exhaust ventilation (e.g., booths for sputum induction or administration of aerosolized medication) is another example of source control.

# Standard Precautions.
A group of infection prevention practices that apply to all patients, regardless of suspected or confirmed diagnosis or presumed infection status. Standard Precautions is a combination and expansion of Universal Precautions 780 and Body Substance Isolation 1102 . Standard Precautions is based on the principle that all blood, body fluids, secretions, excretions except sweat, nonintact skin, and mucous membranes may contain transmissible infectious agents. Standard Precautions includes hand hygiene, and depending on the anticipated exposure, use of gloves, gown, mask, eye protection, or face shield. Also, equipment or items in the patient environment likely to have been contaminated with infectious fluids must be handled in a manner to prevent transmission of infectious agents, (e.g., wear gloves for handling, contain heavily soiled equipment, properly clean and disinfect or sterilize reusable equipment before use on another patient).

# Surgical mask.
A device worn over the mouth and nose by operating room personnel during surgical procedures to protect both surgical patients and operating room personnel from transfer of microorganisms and body fluids. Surgical masks also are used to protect healthcare personnel from contact with large infectious droplets (>5 m in size). According to draft guidance issued by the Food and Drug Administration on May 15, 2003, surgical masks are evaluated using standardized testing procedures for fluid resistance, bacterial filtration efficiency, differential pressure (air exchange), and flammability in order to mitigate the risks to health associated with the use of surgical masks. These specifications apply to any masks that are labeled surgical, laser, isolation, or dental or medical procedure (). Surgical masks do not protect against inhalation of small particles or droplet nuclei and should not be confused with particulate respirators that are recommended for protection against selected airborne infectious agents, (e.g., Mycobacterium tuberculosis).