In May 2023, the Shelby County Health Department identified a legionellosis outbreak among attendees of the same church. Epidemiologic, environmental, and laboratory investigations were initiated. Laboratory-based surveillance identified persons with a positive Legionella test result. Church attendees were surveyed about attendance, symptoms of legionellosis, and water exposures. Environmental assessment of the church included asking about recent water management practices and collecting samples from water sources for culture. The health department identified 16 church attendees who had legionellosis symptoms. Of these, 9 (56%) had positive laboratory test results for Legionella pneumophila, 7 were hospitalized, and none died. Our investigation revealed that recent changes in water management practices at the church included renewed operation of a large, jetted baptismal font. In all, 17 environmental samples were collected; of these samples, 5 (including 4 from the baptismal font) had L. pneumophila serogroup 1 isolated by culture. Environmental sampling was crucial in identifying the baptismal font as the likely source of L. pneumophila. Education about water management and remediation recommendations were provided to staff at the church.
Keywords: Legionella pneumophila; community education; legionellosis outbreak; serogroup 1; water management.