OUTBREAK INVESTIGATIONS

Epidemic nosocomial infections are defined as hospital-acquired infect ions that represent an increase in incidence over expected rates. Epid emic-associated infections usually are clustered temporally or geograp hically, suggesting that the infections are from a common source or ar e secondary to increased person-to-person transmission. Epidemics are important, because they account for a substantial percentage of nosoco mial infections. Furthermore, if infection control personnel thoroughl y investigate outbreaks of nosocomial infections, they may identify ne w agents, reservoirs, or modes of transmission.