Epidemiologic characteristics of an outbreak of serogroup C meningococcal disease and the public health response.

An outbreak of serogroup C meningococcal disease occurred in six counties in the State of Washington from January 1989 through mid-1991. This report describes epidemiologic data collected from hospitals and health departments, the results of multilocus enzyme electrophoresis of isolates, and the vaccination of high-risk populations in one county. A total of 45 confirmed or probable cases (10 per 100,000 population) occurred. Infants younger than age 1, Hispanics and American Indians, and low-income populations had high attack rates. Nine (20 percent) patients died. The predominant enzyme type, ET-22, had not been detected previously in Washington. More than 22,000 persons were vaccinated in one of the counties. Major challenges to health care personnel included deciding when and where to employ vaccination, obtaining sufficient vaccine, and responding to public anxiety.