PONTIAC FEVER: ISOLATION OF THE ETIOLOGIC AGENT (LEGIONELLA PNEUMOPHILA) AND DEMONSTRATION OF ITS MODE OF TRANSMISSION

Abstract

Pontiac fever, a unique epidemiologic form of legioneliosis, is characterized by a short (one- to two-day) incubation period and a self-limited grippe-like illness without pneumonia. In 1968, the first documented outbreak of this syndrome affected persons who had entered a health department building in Pontiac, Michigan. Epidemiologic analyses clearly implicated an airborne agent and suggested that evaporative condenser water aerosols being disseminated by a defective air conditioning system played a key role in the outbreak. Guinea pigs that were exposed in the building and to laboratory aerosois of evaporative condenser water developed bronchopneumonia. Legionella pneumophila (serogroup 1) was isolated from the exposed guinea pigs' lungs. Paired acute and convalescent serum specimens from 37 patients were tested by the indirect fluorescent antibody technique using L. pneumophila serogroup 1 antigen, and 31 (84%) had rises in titer from <32 to ≥64.