MAJOR FOCUS OF LEGIONNAIRES DISEASE IN BLOOMINGTON, INDIANA

Thirty-nine cases of Legionnaires' disease in a 16-mth period were identified in visitors to and residents of Bloomington, Indiana. Thirty-five patients had spent at least 1 night at the Indiana Memorial Union in the 2 wk before coming ill. Five of 32 sporadic cases nationwide between 1 January and 31 March 1978 were retrospectively shown to be in persons who had recently visited the Union. The risk of acquiring Legionnaires' disease as a Union visitor was at least 17 times greater than that for Bloomington residents 20 yr or older. Employees who had worked at the Union 5 yr or longer were more likely to be seropositive than workers in other Bloomington hotels. Legionnaires' disease bacterium was isolated from 5 environmental sites in Bloomington. A cooling tower may have been involved in disease spread, but it was not the only source. Hypochlorite solution was added to cooling tower water as a precautionary measure; however, 1 case was confirmed in a man with Union exposure 9 days after hypochlorite treatment had begun.