Outbreak of Legionnaire's Disease Linked to a Decorative Fountain by Molecular Epidemiology

The incubation period of Legionnaires' disease in five patients was traced to attendance at conventions in a hotel in the Orlando, Florida, area between January 6 and February 2, 1992. The five case patients (mean age, 69 years) were older than 55 randomly chosen controls (mean age, 53 years) who had also attended one of the same conventions (p = 0.007). All case patients were males, as were 40% of the controls (p = 0.01). No significant differences in exposures were found between case patients and controls, but all case patients and 65% of the controls reported exposure to a decorative fountain in the hotel lobby. Water from the fountain was the only one of 55 environmental specimens to test positive for Legionella. Both the environmental isolate and the only clinical isolate were Legionella pneumophila serogroup 1, with identical patterns identified on monoclonal antibody subtyping and pulsed-field gel electrophoresis (PFGE) of genomic restriction fragments. The fountain's recirculating system had been irregularly maintained, and water in the fountain may have been heated by submersed lighting. These findings demonstrate the utility of monoclonal antibody subtyping and PFGE of genomic restriction fragments in assessing the significance of environmental isolates of L. pneumophila, especially when other epidemiologic findings are inconclusive. They also show that decorative fountains may be a potential source of infection with L. pneumophila, and emphasize the need for standard maintenance and disinfection procedures.