A countywide outbreak of pertussis: initial transmission in a high school weight room with subsequent substantial impact on adolescents and adults.

Objective: To describe a large communitywide pertussis outbreak where aggressive diagnostic and treatment measures were used to control the outbreak.

Design: Retrospective analysis, May 2003 through February 2004.

Setting: Fond du Lac County, Wisconsin (population 98,882).

Evaluation of polymerase chain reaction and culture for diagnosis of pertussis in the control of a county-wide outbreak focused among adolescents and adults.

During a large pertussis outbreak, culture and polymerase chain reaction (PCR) were used to identify 149 case patients; of these case patients, 79 had positive PCR and culture results, 59 had positive PCR results and negative culture results, 11 had negative PCR results and positive culture results (10 PCR-negative, culture-positive specimens were collected < or = 14 days after illness onset). PCR and culture of samples obtained < or = 2 weeks after illness onset and PCR of samples obtained > 2 weeks after illness onset proved to be most diagnostically useful.