CONCURRENT OUTBREAKS OF PERTUSSIS AND MYCOPLASMA-PNEUMONIAE INFECTION- CLINICAL AND EPIDEMIOLOGIC CHARACTERISTICS OF ILLNESSES MANIFESTED BY COUGH

Concurrent outbreaks of illnesses that were manifested by cough and th at were suspected to be due to Bordetella pertussis and Mycoplasma pne umoniae infection were investigated in a midwestern town in Illinois. Three studies were conducted: questionnaires on the clinical and epide miological characteristics of illness were administered to patients; s erological tests were performed to confirm the presence of each pathog en and to develop case definitions for each illness; and case definiti ons were applied to responses to a mail-in questionnaire for estimatin g the magnitude of both outbreaks. In 135 cases of suspected pertussis and 42 cases of suspected mycoplasmal infection, subjects had a cough for greater than or equal to 14 days (the pertussis outbreak case def inition). Among 20 laboratory-confirmed cases, a cough for greater tha n or equal to 14 days had a specificity of 20% for pertussis, and a co ugh for greater than or equal to 28 days plus whoop and/or vomiting ha d a specificity of 90% for pertussis. Six hundred-seventeen pertussis cases per 100,000 population and 1,179 cases of M. pneumoniae infectio n per 100,000 population occurred. In this setting, the standard outbr eak case definition for pertussis lacked adequate specificity to disti nguish pertussis from mycoplasmal infection. The magnitude of each out break was greater than the number of reported cases suggested.