Patients, needles, and health care workers.

The risk of transmission of blood-borne pathogens in the health care environment is determined by three main factors: the nature and frequency of exposure to blood or body fluids, the risk of transmission of infection after a single exposure to the pathogen, and the prevalence of infected and susceptible patients and health care workers. In this article, all three parts of the risk equation are examined and brought into focus by addressing the risks and pathologic consequences of infection with four important blood-borne viruses--the human immunodeficiency virus (HIV), hepatitis B (HBV), hepatitis C (HCV), and the cytomegalovirus (CMV). The current approaches to management of occupational exposures to blood-borne pathogens and prospects for prevention are discussed.