Pontiac fever associated with a whirlpool spa.

In March 1981, an outbreak of 34 cases of Pontiac fever occurred among 74 members of a social club who visited an inn in south-central Vermont. Environmental and epidemiologic investigations were done to identify the causes of the illness. The outbreak of Pontiac fever was most likely caused by L. pneumophila, serogroup 6, which was identified in a whirlpool spa at the inn. This is the first reported instance of an outbreak of Pontiac fever associated with a whirlpool spa.