Benchmarking for prevention: the Centers for Disease Control and Prevention's National Nosocomial Infections Surveillance (NNIS) system experience.

Healthcare-associated infections are a major cause of morbidity and mortality at hospitals in the United States. Surveillance of these infections identifies secular trends and provides data upon which prevention interventions can be based in order to improve patient safety. National surveillance of healthcare-associated infections was initiated in the United States in 1970. Since that time, the Centers for Disease Control and Prevention's (CDC) National Nosocomial Infections Surveillance (NNIS) system has provided standardized methods for collecting and comparing healthcare-associated infection rates and the national benchmark infection rate data for inter- and intra-hospital comparisons. The surveillance methods used and results of the implementation of these methods are reviewed. The number of hospitals participating in the CDC's national surveillance of healthcare-associated infections has grown from approximately ten to 20 hospitals in 1970 to over 300 hospitals in 2002. Over the years, NNIS system participants have used standardized definitions, standardized surveillance component protocols, risk stratification for calculation of infection rates and provided national benchmark infection rates for inter- and intra-hospital comparisons. These methods have resulted in a significant reduction in bloodstream infections, urinary tract infections and pneumonia in intensive care unit (ICU) patients and surgical site infections in surgical patients. The NNIS data show that national surveillance of healthcare-associated infections combined with an intervention prevention program can reduce infection rates, reduce morbidity and mortality and improve patient safety. Establishment of such healthcare-associated infection surveillance and prevention systems in countries throughout the world should be a priority.