Laboratory-confirmed shigellosis in the United States, 1989-2002: epidemiologic trends and patterns.

During 1989-2002, a total of 208,368 laboratory-confirmed Shigella infections were reported to the Centers for Disease Control and Prevention. Shigella sonnei accounted for 71.7%, Shigella flexneri accounted for 18.4%, Shigella boydii accounted for 1.6%, and Shigella dysenteriae accounted for 0.7% of infections; for 7.6%, no serogroup was reported. National incidence rates ranged from 7.6 cases per 100,000 persons in 1993 to 3.7 cases per 100,000 persons in 1999. Incidence rates for S. boydii, S. dysenteriae, and S. flexneri decreased over the 14-year period by 81%, 83%, and 64%, respectively; S. sonnei rates only decreased by 8%. The highest rates were reported from western states (10.0 cases per 100,000 persons) and among children 1-4 years of age (20.6 cases per 100,000 persons). The female-male S. sonnei incidence rate ratio among 20-39-year-old adults decreased from 2.3 during 1989-1999 to 1.4 during 2000-2002. Approximately 1% of isolates were from extraenteric sources; 0.25% were from blood. S. sonnei remains an important cause of diarrhea in the United States. Prevention efforts that target high-risk groups are needed.