Two more people have died in the Upper East Side Legionnaires’ disease cluster, pushing the death toll to nine.
Health Commissioner Dr. Alister Martin announced the grim milestone Friday, confirming that two patients diagnosed weeks earlier had succumbed to the illness. The cluster, centered on Carnegie Hill and Yorkville in Manhattan, has now killed more people than the 2025 Harlem outbreak that left seven dead.
“I’m saddened to share that 2 more people have died in connection with the UES Legionnaires’ disease cluster,” Martin said in a statement.
“We mourn each loss, and our hearts are with their loved ones.”
Martin said the source of the outbreak has been eliminated, though the city has not publicly identified a specific building or cooling tower responsible. One person remains hospitalized, according to the Department of Health.
The announcement came as the city officially declared the outbreak over on July 31, saying no new cases had been diagnosed after July 21 and that the incubation period for new infections had passed. The final tally stands at 92 diagnosed cases across ZIP codes 10028, 10075, and 10128, with nine deaths.
The 2025 Harlem outbreak, which also involved a cooling-tower cluster, had been the city’s most deadly recent Legionnaires’ event until now. That cluster saw 18 cases and seven deaths, with investigators eventually matching bacteria from a patient specimen to a cooling tower at NYC Health + Hospitals/Harlem.
The Upper East Side investigation tested 183 cooling towers at 160 buildings. Initial PCR screening found Legionella genetic material in 77 towers at 75 buildings, while slower confirmatory culture testing identified live bacteria in 59 towers at 58 buildings. All 82 towers that tested positive in either method were ordered cleaned and disinfected, and the city reported all remediation was completed.
Enforcement data revealed widespread compliance problems. The Health Department found violations at 60 percent of towers with positive outbreak tests, issuing more than 110 violations total. Those included more than 15 public health hazards, more than 50 critical violations, and more than 40 general violations. At 1520 York Avenue, which tested PCR positive and later culture negative, inspectors found nine public health hazard violations and issued $9,000 in fines related to testing requirements and maintenance plans.
The compliance picture shifted dramatically after the city began publishing results. On July 10, the Health Department released its preliminary list of PCR-positive buildings. The day after, 74 percent of towers eventually inspected had submitted records showing they met the city’s monthly Legionella testing requirement. By July 24, that figure had climbed to 97 percent. Among all 183 towers sampled, compliance rose from 73 percent to 92 percent over the same two weeks.
Whole genome sequencing to compare patient bacteria against environmental samples is expected to be complete by the end of August. That DNA fingerprinting represents the best chance to definitively link specific illnesses to a specific source, if such a match exists.
In the viral moment that launched this summer’s crisis, the Health Department announced on July 2 that two confirmed cases in Carnegie Hill and Yorkville had triggered a formal cluster investigation. The city rapidly expanded the zone, adding ZIP code 10075 by July 5 and advising visitors to the east side of Central Park between East 76th and East 97th Streets to monitor for symptoms. Case counts mounted quickly: 59 diagnosed by July 12, 82 by July 21, and 92 by July 29. The first death was reported July 21, with the toll rising to seven by July 30 before Friday’s announcement of two additional fatalities.
The outbreak prompted an unusually intensive and public response, including the unprecedented release of address-level preliminary PCR findings for 76 properties. Notable locations on the positive list included the Metropolitan Museum of Art, the Solomon R. Guggenheim Museum, the Chapin School, the Dalton School, and Whole Foods Market’s Upper East Side location. The city repeatedly emphasized that presence on the list did not mean a property caused illness or contained viable bacteria at the time of testing.