31 Upper East Side buildings test positive for Legionella bacteria

The New York City Health Department said 31 Upper East Side buildings with cooling towers tested positive for Legionella in an initial PCR screening, and all 31 were ordered to clean and disinfect immediately. The agency said 19 buildings had already finished remediation and 12 were expected to complete it by July 11. A positive PCR result does not prove a building is the outbreak source because the test can detect dead bacteria as well as live bacteria.

The outbreak had already grown to 54 cases, with 18 people hospitalized and no deaths reported. The affected area includes Carnegie Hill and Yorkville, in ZIP codes 10028, 10128 and 10075. City health officials also said it remained safe to shower, drink tap water, bathe, cook and use air conditioners in those ZIP codes because the illness is tied to cooling towers, not the plumbing system inside homes.

The Solomon R. Guggenheim Museum, at 1071 Fifth Ave., said its cooling tower tested positive earlier in the week and that it performs monthly testing and cleaning with third-party experts. The museum said the city’s required remediation was taken immediately, and UAW Local 2110 said it was satisfied with the response and that the tower would be retested the following week.

On July 7, Mayor Zohran Mamdani’s administration said it would publicly release addresses of buildings whose cooling towers test positive in the city’s initial PCR screen, and require immediate drain-clean-disinfect work instead of waiting for confirmatory culture results. The Health Department said it mobilized more than 100 staff members for the Upper East Side investigation. Culture testing on sampled towers can take up to two weeks and is needed to determine whether live Legionella is present.

Gothamist’s count put 203 active cooling towers in the three ZIP codes covering the affected area, compared with the city’s count of 160, and 55 percent of those towers had 2026 Legionella test results on file. About half had gone more than a year without a city inspection. New York’s worst Legionnaires’ outbreak came in the South Bronx in 2015, when 138 cases and 16 deaths were linked to a single cooling tower, and the city later strengthened its cooling-tower rules again in 2025 after a Central Harlem cluster.