REDUCTION IN THE INCIDENCE OF HUMAN LISTERIOSIS IN THE UNITED-STATES - EFFECTIVENESS OF PREVENTION EFFORTS

Background.-Food-borne transmission is now recognized as a major cause of human listeriosis. Objective.-To assess the impact of prevention e fforts, listeriosis rates before interventions were initiated in 1989 were compared with more recent rates (1990 through 1993). Design.-From 1989 through 1993, multistate, laboratory-based active surveillance w as conducted to identify all cases in which Listeria monocytogenes was isolated from cultures or ordinarily sterile sites in an aggregate po pulation of more than 19 million. Setting.-All laboratories serving ac ute care hospitals in up to nine surveillance areas in the United Stat es. Interventions.-In 1989, a well-publicized case report of listerios is linked to processed poultry led US regulatory agencies to enforce a ggressive food monitoring policies and prompted industry to invest in cleanup efforts. In May 1992, consumer guidelines for listeriosis prev ention were disseminated. Outcome Measures.-Cases of perinatal and non perinatal listeriosis. Results.-The rate of listeriosis decreased in a ll surveillance areas. Projection of these rates to the US population suggests an estimated 1965 cases and 481 deaths occurred in 1989 compa red with an estimated 1092 cases and 248 deaths in 1993, a 44% and 48% reduction in illness and death, respectively. Among adults 50 years o f age and older, rates declined from 16.2 per 1 million in 1989 to 10. 2 per 1 million in 1993 (P=.02). Perinatal disease decreased from 17.4 cases per 100 000 births in 1989 to 8.6 cases per 100 000 births in 1 993 (P=.003). Three serotypes (1/2a, 1/2b, and 4b) of L monocytogenes accounted for more than 96% of cases during each year of the study (19 89 through 1993). Conclusions. The incidence of listeriosis in study a reas was substantially lower in 1993 than in 1989. The temporal associ ation of this reduction with industry, regulatory, and educational eff orts suggests these measures were effective.