Guide F --

Environmental Control of Smallpox Virus

Guide F. Environmental Control of Smallpox Virus

# Purpose:

This document provides general guidance on environmental infection
control and decontamination for use in any setting where care is given
to smallpox patients. This information will be beneficial to:

-   Healthcare workers,

-   Housekeeping and laundry personnel,

-   Mortuary personnel and morticians,

-   Public health officials,

-   Emergency responders in handling cases of smallpox, and

-   Persons who manage the treatment and disposal of regulated medical
    waste.

# Introduction:

Variola virus is a member of the genus *Orthopoxvirus* within the family
*Poxviridae.* Poxviruses are large, brick-shaped, enveloped viruses with
a double-stranded DNA genome. Of the four orthopoxviruses known to
infect humans, variola virus (major and minor) produces the most
significant clinical disease (smallpox).

# Transmission and Engineering Controls:

Smallpox is transmitted routinely person-to-person (a form of direct
contact) via inhalation of variola virus present in droplets generated
from the respiratory tract of infected, symptomatic patients. Since
disease transmission is via direct contact, infection control and
prevention measures are based primarily on contact and droplet
precautions.^1^ Historically, secondary transmission of infection has
been limited to susceptible contacts in the immediate vicinity of
patients. Patients become infectious at onset of their rash. Lesions
develop primarily on the skin soon after onset and eventually form scabs
that can slough off. Viable viruses can be present in these scabs, and
the protein material of the scab can protect the viruses from
desiccation. Poxviruses shed during the course of infection therefore
tend to be more resistant to the effects of drying compared to other
enveloped viruses (e.g., influenza viruses, rubella virus). Poxviruses
(e.g., vaccinia virus, variola virus) are tightly bound with the fibrin
matrices of the scab, however, and this limits the efficiency of virus
transfer from environment to persons via reaerosolization.^2^ There are
limited reports of airborne spread of variola virus in healthcare
facilities and laboratories^3,\ 4^ and reaerosolized transmission from
fabric or bedding fomites.^5,\ 6^ The mechanisms of virus spread as
described in these reports, however, may represent potentially important
exceptions to the usual mode of transmission. Additional factors present
in these situations (e.g., enhanced efficiency of viral shedding from
oral and pharyngeal lesions, poorly engineered facility ventilation) may
have contributed to and facilitated viral dispersion in ways that might
not be consistently duplicated in contemporary healthcare facilities.^3^

A properly engineered heating, ventilation, and air-condition (HVAC)
system can minimize the possibility of airborne spread of variola virus
in facilities providing care for smallpox patients. Placing smallpox
patients in airborne infection isolation (AII) rooms (i.e., rooms under
negative air pressure relative to the corridor or other adjacent space)
can help to limit distribution of virus in the air.^7^ Existing AII
rooms in healthcare facilities need not be modified beyond the current
engineering specifications.^8^ A more in-depth discussion of variola
virus transmission can be found in [Guide A---Smallpox Surveillance and
Case Reporting; Contact Identification, Tracing, Vaccination, and
Surveillance; and Epidemiologic
Investigation](http://www.bt.cdc.gov/agent/smallpox/response-plan/files/guide-a.pdf)

Variola virus could hypothetically be used as a weapon either through
airborne dispersion or through intentionally infecting one or more
persons and encouraging them to circulate among groups of people,
thereby exposing these contacts to variola virus infection. If
introduced into the air, it is likely that the virus would be
inactivated within 24 hours, and certainly would not be present in the
environment by the time any cases might occur 7-17 days later. The
expected outcome resulting from this form of release would most likely
be large numbers of cases with clustered onsets. Establishing
epidemiologic association among these cases could be problematic,
depending on the site and extent of virus dispersion. If introduced
through intentionally infected persons, the origin of the virus (i.e.,
the index case) and the extent of the outbreak could likely be tracked
using standard epidemiologic and laboratory methods.

# Occupational Issues:

The following activities should be limited preferably to persons with
active immunity to smallpox:

-   Patient-care activities,

-   Laundry ,

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-   Decontamination procedures, and

-   Mortuary procedures.

Refer to Guide B---Vaccination Guidelines for State and Local Health
Agencies [part
1](http://www.bt.cdc.gov/agent/smallpox/response-plan/files/guide-b-part1of3.pdf),
[part
2](http://www.bt.cdc.gov/agent/smallpox/response-plan/files/guide-b-part2of3.pdf),
and [part
3](http://www.bt.cdc.gov/agent/smallpox/response-plan/files/guide-b-part3of3.pdf)
for information on vaccination strategies for workers who provide these
services and for those not involved with these functions. Personal
respiratory protection (i.e., N95 respirators) may be indicated for
those workers who provide direct care to smallpox patients. Whenever
possible, disposable versions of PPE should be used as appropriate and
discarded after use as per routine medical waste disposal practices.^9^
All personnel should adhere to hand hygiene practices as per current
recommendations.^10^ Refer to [Guide C part one---Infection Control
Measures for Healthcare and Community
Settings](http://www.bt.cdc.gov/agent/smallpox/response-plan/files/guide-c-part-1.pdf)
for information about the appropriate types of PPE and indications for
their use.

# Decontamination and Disinfection:

In general, large enveloped viruses have less intrinsic resistance to
inactivation by either physical or chemical methods of disinfection
compared to nonenveloped viruses and many types of bacteria or fungi.
The envelope surrounding the core particle of a large virus (e.g.,
variola virus) contains lipids, and this biochemical property renders
this and other enveloped viruses particularly sensitive to chemical
disinfection (Figure 1).

Figure 1. Relative Resistance of Microorganisms to Chemical
Disinfection\*

## (*Most Resistant*) {#most-resistant .unnumbered}

## Bacterial endospores {#bacterial-endospores .unnumbered}

⇓

## Mycobacteria {#mycobacteria .unnumbered}

⇓

## Non-lipid and small viruses {#non-lipid-and-small-viruses .unnumbered}

(e.g., Norwalk virus, polio virus)

⇓

## Fungi {#fungi .unnumbered}

⇓

## Vegetative bacteria {#vegetative-bacteria .unnumbered}

⇓

## Lipid or medium sized viruses {#lipid-or-medium-sized-viruses .unnumbered}

(e.g., herpes simplex virus \[HSV\], hepatitis B virus \[HBV\],
hepatitis C virus \[HCV\],

human immunodeficiency virus \[HIV\], varicella-zoster virus \[VZV\],

vaccinia virus, variola virus )

### *(Least Resistant)* {#least-resistant .unnumbered}

\* Note: Modified from reference #11

There are no disinfectant products registered by the U.S. Environmental
Protection Agency (EPA) specifically for the inactivation of variola
virus on surfaces, nor have any products been evaluated for this purpose
using this specific virus in potency testing. It has been established,
however, that viruses with biophysical and biochemical properties
similar to those of variola virus (i.e., vaccinia virus) are readily
inactivated by a variety of active ingredients found in EPA-registered
chemical germicides that provide low- or intermediate-level disinfection
during general use (Table 1).^12,\ 13^ If a manufacturer has submitted
data to EPA showing that the product inactivates vaccinia virus, and the
EPA has accepted those data and approved such a claim (as it has for a
number of products), then the product's label would bear specific use
directions for killing vaccinia virus on environmental surfaces. The
empiric presumption is that such products would be expected to have
sufficient potency to inactivate variola virus on nonporous surfaces.

**Table 1. Chemical Inactivation of Vaccinia Virus on Surfaces:**

**Inactivation After 10 Minutes Contact Time at Room Temperature^a^**

+-----------------------------------+-----------------------------------+
| ### Chemical Disinfectant {#c     | ### Minimum                       |
| hemical-disinfectant .unnumbered} |  Concentration to Achieve Inactiv |
|                                   | ation {#minimum-concentration-to- |
|                                   | achieve-inactivation .unnumbered} |
+-----------------------------------+-----------------------------------+
| #####  Chemicals Used on E        |                                   |
| nvironmental Surfaces for Low- or |                                   |
|  Intermediate-Level Disinfection  |                                   |
| {#chemicals-used-on-environmental |                                   |
| -surfaces-for-low--or-intermediat |                                   |
| e-level-disinfection .unnumbered} |                                   |
+-----------------------------------+-----------------------------------+
| #### Ethyl alc                    | 40%                               |
| ohol {#ethyl-alcohol .unnumbered} |                                   |
+-----------------------------------+-----------------------------------+
| Isopropyl alcohol                 | 30%                               |
+-----------------------------------+-----------------------------------+
| Benzalkonium chloride             | 100 ppm^b^                        |
+-----------------------------------+-----------------------------------+
| #### Sodium hypochlorite {        | 200 ppm                           |
| #sodium-hypochlorite .unnumbered} |                                   |
+-----------------------------------+-----------------------------------+
| *Ortho*-phenylphenol              | 0.12%                             |
+-----------------------------------+-----------------------------------+
| Iodophor                          | 75 ppm                            |
+-----------------------------------+-----------------------------------+

a.  Modified from references #12, 13, and 14

b.  ppm: Parts per million

c.  Use of this chemical in health care is limited.

Concentrations of the chemicals listed in Table 1 are lower than those
commonly used in healthcare applications. It is therefore expected that
manufacturer-recommended use-concentrations of EPA-registered germicides
will be adequate for routine disinfection of cleaned environmental
surfaces for management of smallpox care areas. The nature and extent of
surface contamination will dictate the level of disinfection (i.e.,
low-level or intermediate-level) needed to make the surface safe to
handle or use. It is also expected that high-level disinfectants or
liquid chemical sterilants cleared by the U.S. Food and Drug
Administration (FDA) for the purpose of achieving high-level
disinfection of semi-critical instruments and devices will be effective
at inactivating vaccinia virus and variola viruses. All sterilization
methods currently cleared by FDA for medical instruments and devices
will also inactivate these viruses. Use of high-level disinfectants or
liquid chemical sterilants on large environmental surfaces (e.g., table
tops, floors, walls) is not indicated under any circumstances.

# Environmental Infection Control of Smallpox:

When developing a strategy for the environmental control of variola
virus, the following elements should be included:

1.  Control measures to reduce viral contamination on fabrics, clothing,
    and bedding,

2.  Cleaning and disinfection of reusable equipment,

3.  Cleaning and appropriate reprocessing of medical instruments,

4.  Cleaning and decontamination of large environmental surfaces,

5.  Regulated medical waste containment, treatment, and disposal, and

6.  Indications (if any) for decontamination of air space in rooms or
    vehicles.

**1. Laundry: Textiles and Bedding:**

Textiles and fabrics (e.g., protective clothing, bed linens, clothing)
from patients and their immediate contacts should be handled with
minimum agitation to avoid contamination of air, surfaces, and
persons.^15^ This prevents the dispersion of potentially contaminated
sloughed-off scabs and skin squames into the air. Textiles and clothing
should be bagged or contained at the point of use in accordance with
Occupational Safety and Health Administration (OSHA) regulations.^9^
These items should not be sorted prior to laundering. Most, if not all
forms of containment used for routine healthcare laundry are acceptable
for containing textiles and fabrics generated in care areas for smallpox
patients. Wet textiles should be bagged first and then placed in a
leak-proof container. Reusable fabric laundry bags commonly used for
laundry transport can be laundered along with the clothing and other
fabrics. The use of a water-soluble bag is another option for minimizing
direct contact and manipulation of these fabrics and clothing prior to
washing. If laundry is transported to an off-site facility, the
procedures that are currently used for transporting and safe handling of
contaminated textiles off-site will be adequate for these situations.
Laundry should be labeled in such a way that laundry staff should be
prompted to wear appropriate PPE and handle potentially contaminated
laundry with a minimum of agitation.^9^

The laundry area in a healthcare facility that receives potentially
contaminated textiles and clothing should be set at negative air
pressure as per normal operating standards, and be physically separate
from the area where clean laundry is dried, folded, and packed for
transport and distribution.^8^

Textiles and fabrics from care areas for smallpox patients can be
laundered using routine protocols for healthcare facilities (i.e., hot
water \[71ºC or 160°F\] washing with detergent and bleach and hot air
drying).^7,\ 11^ No special laundering protocols are needed, nor is it
necessary to launder materials from smallpox care areas separately from
laundry generated elsewhere in the facility. If contaminated clothing
and bed linens are to be washed at home, use the hot water cycle at the
highest temperature possible with detergent followed by hot air drying.
The use of chlorine bleach during hot-water washing can provide
additional measure for safety. The use of cold water washing has not
been evaluated with respect to inactivation of variola virus. If no
other wash cycles other than cold water are available, use detergents
and laundry additives that are specifically formulated for cold-water
washing and dry using a hot air cycle for the dryer.^7^

**2. Reusable Medical Equipment:**

The surfaces of reusable medical equipment should be cleaned and then
subjected to either low- or intermediate-level disinfection with an
EPA-registered chemical germicide in accordance with label instructions.
Current protocols and procedures for cleaning and disinfection need not
be changed.^7,\ 11^

**3. Medical Instruments:**

Disposable medical instruments and patient-care devices should be placed
in containment for safe handling and discarded as per state regulations
for the routine handling of medical waste. All reusable medical
instruments should be cleaned after use as per standard protocols. These
instruments should then be either sterilized or subjected to high-level
disinfection depending on their intended use as per the Spaulding
classification.^11^ There is no need to presoak the instruments unless
the instruments cannot be cleaned and reprocessed immediately after use.
In this situation, water or saline with or without detergents are
adequate soaking agents.

**4. Environmental Surfaces:**

Environmental surfaces that are touched frequently by hand can be
cleaned and subjected to low- to intermediate-level disinfection with
EPA-registered chemical germicides according to label instructions.^7^
Large housekeeping surfaces such as floors and tabletops can be cleaned
using an EPA-registered detergent disinfectant according to
manufacturer's instructions.^7^ There is no evidence for transmission of
variola virus from nonporous surfaces. Therefore, there is no indication
to use extraordinary procedures to clean and disinfect the interior
surfaces of ambulances or other spaces occupied by smallpox patients.
Routine approaches for cleaning and disinfection are adequate in these
areas.

Current procedures and schedules can be used for management of floors
and furniture.^7^ Use a vacuum cleaner equipped with a high efficiency
particulate air (HEPA) filter for cleaning carpeted floors or
upholstered furniture. Disinfection of the vacuum cleaner is not
required when a HEPA filter is properly installed and remains intact
during use. Full vacuum cleaner bags can be placed in another closable
container and discarded as a routine solid waste.^7^ If carpets and
upholstered furniture require cleaning to remove visible soil,
commercially available products for this purpose are acceptable for use
as per usual.

5\. Regulated Medical Waste:

Regulated medical waste should be placed in containment, subjected to a
decontamination treatment, and discarded in accordance with medical
waste regulations of the state or other appropriate jurisdiction. This
includes the use of offsite medical waste treatment services. However,
if healthcare facilities have the capability of treating/decontaminating
medical waste onsite, this capacity should be the first option for
medical waste management.^7^ All currently approved methods of medical
waste decontamination can be expected to inactivate pox viruses.

State health departments or other authorities having jurisdiction should
partner with state environmental agencies to develop appropriate
policies and/or regulations to ensure the safe disposal of treated
regulated medical wastes. These agencies should provide assurance to
landfill operators that these treated wastes will not pose significant
risk of smallpox exposure to either the landfill workers or to the
general public. There is no scientific basis for refusing landfill
disposal of these treated wastes.

Many, if not all states, consider anatomical and pathological wastes as
regulated medical wastes, but the remains of a decedent are usually
excluded from this category. Incineration is one option for effectively
treating anatomical and pathological wastes prior to disposal; other
treatment options may be allowed for this waste category as per state
regulations or the regulations of the authority having jurisdiction.
Remains can be safely managed in mortuary settings using the current
practices of barrier protection, Standard precautions, and other
appropriate safety procedures during embalming or otherwise preparing
the body for cremation (e.g., safe handling and disposal of embalming
chemicals, proper ventilation, environmental surface clean-up and
disinfection).

The public health authority may choose to exercise the powers regarding
the safe disposal of human remains as outlined in Section 504 of the
Model State Emergency Health Powers Act if it is determined that a state
of public health emergency exists.^16^

6\. Indications for Decontamination of Air Space in Rooms or Vehicles:

There is no evidence to support air space decontamination of rooms,
facilities, or vehicles (e.g., fumigation). Therefore, fumigation is not
indicated for environmental control of variola virus. In controlled
laboratory dispersion studies using aerosolized vaccinia virus,
infectious virions were rapidly inactivated in the environment, such
that only 10% viable particles were detectable 24 hrs after the
release.^17^ Factors affecting the rate of viral inactivation in this
study included:

-   Temperature,

-   Humidity, and

-   Exposure to ultraviolet irradiation (i.e. a release outdoors).^17^

An additional laboratory study of variola virus aerosols under
controlled conditions has shown that increasing levels of humidity have
little effect on viral inactivation (biological decay) compared to other
viruses.^18^ In this study, only 10%--30% of viable variola viruses were
recovered from controlled aerosols after 1 hour.

However, by the time cases appear in the community following an aerosol
release, the presumption is that no viable virus would be remaining in
the environment from that release. Additionally, modern HVAC systems and
current engineering specifications for those systems provide for air
cleaning via air changes per hour (ACH).^7^ As stated previously, it is
also unlikely that variola virus embedded in the fibrin material from
scabs will be easily released from this material and dispersed into the
air. If the virus were able to persist in an infectious form in the
environment, then additional cases having no contact with infected
persons would have been identified. This observation was noted in
studies conducted during the smallpox eradication era.^19^

References:

1.  Garner JS, Hospital Infection Control Practices Advisory Committee.
    Guideline for isolation precautions in hospitals. *Infect Control
    Hosp Epidemiol* 1996; 17: 53-80.

2.  Henderson DA, Inglesby TV, Bartlett JG, et al. Smallpox as a
    biological weapon: Medical and public health management. *JAMA*
    1999; 281: 2127-2137.

3.  Wehrle PF, Posch J, Richter KH, Henderson DA. An airborne outbreak
    of smallpox in a German hospital and its significance with respect
    to other recent outbreaks in Europe. *Bull WHO* 1970; 43: 669-679.

4.  Hawkes N. Science in Europe: Smallpox death in Britain challenges
    presumption of laboratory safety. *Science* 1979; 203: 855-856.

5.  Dixon CW. *Smallpox*. J & A Churchill Ltd., London, 1962: p. 1460.

6.  Downie AW, Meiklejohn G, St Vincent L, et al. The recovery of
    smallpox from patients and their environments in a smallpox
    hospital. *Bull WHO* 1965; 33: 615-622.

7.  Centers for Disease Control and Prevention. CDC Guideline for
    Environmental Infection Control in Healthcare Facilities. *MMWR*
    2003; 52: in press.

8.  American Institute of Architects. *Guidelines for Design and
    Construction of Hospital and Healthcare Facilities, 2001*.
    Washington DC; American Institute of Architects Press: 2001

9.  U.S. Department of Labor, Occupational Safety and Health
    Administration. Occupational exposure to bloodborne pathogens, final
    rule. 29 CFR 1910. 1030. *Federal Register* Number range
    CHAPTER1991; 56: 64004-64182.

10. Centers for Disease Control and Prevention. Guideline for hand
    hygiene in healthcare settings. Recommendations of the Healthcare
    Infection Control Practices Advisory Committee and the
    HICPAC/SHEA/APIC/IDSA Hand Hygiene Task Force. *MMWR* 2002; 51
    (RR-16): 1--45. Also at: <http://www.cdc.gov/handhygiene/>

11. Garner JS, Favero MS. Guideline on handwashing and hospital
    environmental control, 1985. *MMWR* 1987; 36 (2S). Also at:
    <http://www.cdc.gov/ncidod/hip/guide/handwash_pre.htm>

12. Prince HN, Prince DL. Principles of viral control and transmission.
    *In:* Disinfection, Sterilization, and Preservation, 5^th^ Ed.,
    Block SS, ed. Philadelphia PA; Lippincott Williams & Wilkins,
    2001: p. 881--917.

13. Klein M, DeForest A. Principles of viral inactivation. *In:*
    Disinfection, Sterilization, and Preservation, 3^rd^ Ed., Block SS,
    ed. Philadelphia PA; Lea & Febiger;1983:p. 422--434.

14. Prince HN. Disinfectant activity against bacteria and viruses: A
    hospital guide. *Particulate Microbiol Control* 1983; 2: 55--62.

15. Joint Committee on Healthcare Laundry Guidelines. *Guidelines for
    Healthcare Linen Services.* Textile Rental Services Association of
    America. Hallendale, FL; 1999.

16. Centers for Disease Control and Prevention. The Model State
    Emergency Health Powers Act. Draft 12/21/02. At:
    http://www.publichealthlaw.net/MSEHPA/MSEHPA2.pdf

17. Harper JG. Airborne microorganisms: Survival test with four viruses.
    *J Hyg* 1961; 59: 479-486.

18. Mayhew CJ, Hahon N. Assessment of aerosol mixture of different
    viruses. *Appl Microbiol* 1970; 20: 313 -- 316.

19. Fenner F, Henderson DA, Arita I, Jerez Z, Ladnyl ID. *Smallpox and
    its Erradication.* World Health Organization (WHO), Geneva
    Switzerland; 1988.