death in the United States (Edmond et al., 1999; Wenzel and Edmond, 2001). CDC estimates that each year nearly 2 million patients in the United States acquire infections in hospitals, and about 90,000 of these patients die as a result (CDC, 2002o).

A number of factors drive the development of nosocomial infections. Foremost in the developed world is advances in health care technology (discussed earlier), for several reasons. The first is improved survival of vulnerable populations, such as the elderly; infants of very low birth weight; and cancer, AIDS, and transplant patients. These individuals are susceptible to germs that would not be harmful to healthy people. Second, greater numbers of invasive procedures—such as placement of indwelling catheters, feeding tubes, ventilators, transplantations, and prosthetic devices— are being performed, allowing microorganisms more direct access to patients’ bloodstreams. Finally, widespread use of antimicrobial drugs in hospitals is resulting in more drug-resistant organisms that are increasingly difficult to treat.

In addition, overcrowded conditions within hospitals and a lack of proper sanitation and hygiene contribute greatly to the transfer of microbes. Studies have shown that potentially pathogenic organisms can be passed on to patients from unclean stethoscopes (Marinella et al., 1997), lab coats (Wong et al., 1991), environmental surfaces, and latex gloves (Ray et al., 2002). However, cross-transmission of microorganisms by the hands of health care workers is considered the main route for the spread of pathogens in hospitals (Pittet et al., 1999). Thus, simple handwashing practices remain the most important preventive measure. Unfortunately, many hospitals are unable to maintain an adequate level of handwashing among health care workers (Vicca, 1999; Saade et al., 2001; Doebbeling et al., 1992; Jarvis, 1994).

Nosocomial outbreaks of Lassa fever and Ebola viral hemorrhagic fever in Africa illustrate the additional complexities of preventing hospital-acquired infections in developing countries. Lassa fever spread in Nigeria in 1989 because scant resources led to needle sharing and reuse of disposable equipment. Overuse of parenteral treatments, inadequate surgical facilities, and poorly trained personnel also fueled the spread of the virus among patients and health care providers (Fisher-Hoch et al., 1995). Similarly, in the absence of appropriate precautions to prevent exposure to blood and other body fluids, hospital outbreaks of Ebola viral hemorrhagic fever in Zaire in 1995 passed from patients to health care workers and to family members who provided nursing care (CDC, 1995b) (see Box 3-15).

Hospitals are perfect breeding grounds for transferring infections among patients, health care providers, and the community. Patients in intensive-care units (ICUs) are at particularly high risk for nosocomial infections as a result of their underlying illness, the multiple invasive proce-



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