A second person has died in the Legionnaires' disease outbreak on Manhattan's Upper East Side, the New York City health department announced on Saturday, July 18, 2026. The outbreak, concentrated in a one-mile area covering ZIP codes 10028, 10075, and 10128, has sickened at least 72 people since the first cases were found on July 2. Nine people were still in the hospital at the time of the announcement; 50 had been sent home. The first death was reported the day before, on July 17.

Health Commissioner Dr. Alister F. Martin said that the data suggests the source of the outbreak "has likely been eliminated." The city took an aggressive approach: on July 14, it ordered 76 buildings to immediately clean and disinfect their cooling towers. Cooling towers are rooftop machines that are part of large building air conditioning systems. They can spread mist that carries bacteria. By July 16, all 76 buildings had finished the cleaning work. The health department said this was the first time New York City ordered every building with a positive test result to clean its cooling tower at the same time.

The numbers support the idea that the source has been dealt with. From July 2 through July 8, the city confirmed an average of more than eight new cases per day. After July 8, that number dropped sharply. From July 10 to July 17, fewer than one new case appeared each day. People whose cases were confirmed recently had actually started feeling sick more than a week earlier, which means they were exposed before the cleanup happened, not after. The health department also said hospital emergency rooms were not seeing alarming trends. Because symptoms can take up to 14 days to appear after someone is exposed, some new cases are still expected even after the source is gone.

Tests found Legionella bacteria — either living or dead — in cooling towers on more than 75 Upper East Side buildings, including museums, private schools, and apartment buildings. Every building with a positive test result was told to clean and disinfect its cooling tower right away, and all of them did. The health department first released a list of 31 buildings on July 11 and later expanded it to the 76 covered by the July 14 order. The department said it will keep inspecting every cooling tower that tested positive and will penalize any building owner who does not follow public health laws. Commissioner Martin also reminded cooling tower operators across the city that they are required in summer to use more biocides, which are chemicals that kill Legionella bacteria.

Legionella bacteria grow in warm water and can multiply in cooling towers, hot tubs, and showerheads. People get sick by breathing in tiny droplets of contaminated water. The disease does not spread from person to person. According to the CDC, Legionnaires' disease kills about 10% of the people who get it.

The Upper East Side outbreak follows a worse one in New York's Harlem neighborhood in August 2025, which killed seven people and sickened more than 100. Both outbreaks were linked to cooling towers in crowded urban neighborhoods. New York City created its cooling tower rules after a 2015 outbreak in the South Bronx killed 12 people. Those rules require building owners to register their towers, test them regularly, and clean them when Legionella is found. The July 14 order was a step up from the usual approach: instead of going building by building, the city told every building with a positive test in the affected area to clean up all at once.

The broader question this outbreak raises is whether the rules already on the books are enough when summer heat makes it easy for bacteria to grow. The Upper East Side is packed with large residential and institutional buildings, each one a potential breeding ground for Legionella. More than 75 buildings tested positive for the bacteria, living or dead, which raises concerns about how many towers were technically following the rules yet still had Legionella in them. The city's decision to order all buildings with positive test results to clean up at the same time, instead of waiting for slower tests that can confirm whether the bacteria are actually alive, reflects a trade-off: the faster test cannot tell living bacteria from dead ones, but waiting for confirmation during an active outbreak means more people get sick.

Commissioner Martin's choice of the word "likely" rather than "confirmed" lines up with the evidence. New cases have dropped, and recently confirmed patients were all exposed before the cleanup. But because symptoms can take up to 14 days to appear, the health department will keep watching for late cases through at least late July. Two deaths out of 72 confirmed cases gives a death rate of about 2.8%, which is below the CDC's 10% figure, though that could change as hospitalized patients either recover or get worse. The Guardian | NYC Health Department