Pontiac fever due to Legionella micdadei from a whirlpool spa: Possible role of bacterial endotoxin

During January 1998, a cluster of illnesses occurred among hotel guests in Wisconsin. Ill persons had been exposed to the hotel's whirlpool spa and sw imming pool. Symptoms included headache, fever, chills, myalgia, shortness of breath, and fatigue. A diagnosis of Pontiac fever was made, based on ser ologic evidence of acute infection with Legionella micdadei. High concentra tions of heterotrophic bacteria were recovered from the spa, despite appare ntly high disinfectant levels. L. micdadei was isolated from the swimming p ool filter and water from the spa after heat enrichment but not from pools and spas at nearby hotels. Water from hotel pools and spas was tested to de termine endotoxin levels; water from the spa of the implicated hotel contai ned the highest concentration of endotoxin (14,400 endotoxin units/mL). Add itional studies are needed to determine the role of endotoxin from legionel lae or other bacteria in the pathogenesis of Pontiac fever.