Chapter 93 Emergent Pandemic Infections

An epidemic of communicable infection that becomes very widespread, affects a whole region or continent, or spreads over several countries and affects many people is termed a pandemic. Three key factors set the conditions for a pandemic: the emergence of a new strain of microorganism; the ability of that strain to infect humans and cause serious illness: that is, the capacity of the organism to cause disease in an infected host (pathogenicity) and the severity of the disease produced (virulence); and the ability of the microorganism to spread easily among humans. Within intensive care units (ICUs) in tertiary care hospitals, factors that decrease transmission of communicable infection between individuals (e.g., reducing the likelihood of contact through isolation), adherence to infection control guidelines, immunization, herd immunity, increasing levels of natural immunity following infection, or depression of agent reservoirs and viability by control programs or seasonal climatic change are offset by the ICU environment, where patients generally have relatively high severity of illness scores and in situ medical devices (e.g., intravascular and urinary catheters), and antimicrobial prescribing remains uncurbed. Compounding the problem are fluctuations in staffing levels, varying degrees of immunization or vaccination among patients, and exposure of patients to health care personnel who move freely among other patients and health care personnel within the institution. The relevance and importance of pandemic preparedness in critical care medicine is underscored by the reality that while there has been a general decrease in the total number of beds in US hospitals during the 1990s, the number of ICU beds has increased during the same period (1). This increase in the numbers of ICU beds suggest larger numbers of critically ill patients are being admitted to the inpatient services with the expected parallel increases in medical device usage and antimicrobial prescribing. The increases in device use and severity of illness scores increase the susceptibility of ICU patients to health care–associated infections—a problem compounded by the crowding that one would expect with the increased patient census in the event of a pandemic. In the wake of a pandemic, tertiary care hospitals with large numbers of beds will, by default, have to provide critical care management for greater numbers of patients in the first instance. The implications of this scenario are serious and complex, and include the increased human and material resources that would be required to manage very sick patients during a pandemic; limited availability of designated areas for cohorting patients who need to be isolated; the logistics of implementing and maintaining adherence to infection control practices and procedures during a pandemic; and the ever present risk of transmission of the pandemic agent among patients and personnel who may be called upon to “float” in other areas of the hospital. This chapter addresses the following true or potentially emergent pandemic infections: • Severe acute respiratory syndrome (SARS)—a true pandemic caused by a previously unrecognized corona virus • Avian influenza—not yet a true pandemic but one which infectious diseases experts believe is imminent and long overdue • Dengue fever and Dengue hemorrhagic fever—a mosquitoborne infection that has insidiously spread across the globe and considered a pandemic by many experts • Tuberculosis—a pandemic caused by Mycobacterium tuberculosis and largely attributable directly to the nearly almost four-decade-long human immunodeficiency virus (HIV) pandemic • Infections caused by Staphylococcus aureus resistant to methicillin group penicillins (methicillin-resistant S. aureus [MRSA])—perhaps the only bacterial microorganism that to reach pandemic proportions in health care settings around the world during the space of three decades • Cholera The importance of being able to address illnesses like Dengue has implications for the management of the newly recognized emerging infections caused by the Middle East respiratory syndrome coronavirus (MERS-CoV) and the Zika virus, which will be discussed briefly at the conclusion of the chapter. The SARS pandemic in 2002 emerged suddenly and unexpectedly, affected health care workers, but was successfully controlled through the application of basic infection control principles and guidelines that had already been established, ratified, and validated. The expected, but not-as-yet seen, emergence of the impending avian influenza pandemic has underscored the importance of preparedness for an event that is so oftentimes decried as “crying wolf” by some and at the same time characterized as “a matter of when rather than if” by others. The fact remains that should an influenza pandemic occur, substantial numbers of persons with the infection will certainly require critical care management, underscoring the need for preparedness from diagnostic, management, control, and preventive perspectives. Although the epidemiology of the respective infections and public health preparedness will be alluded to, this chapter focuses more on the diagnosis and management of the infections, the relevant infection prevention and control interventions for the respective infections, and the obstacles that might be faced by ICU care givers during a pandemic.