New cases of Legionnaires' disease in an outbreak on Manhattan's Upper East Side are slowing, with 60 cases reported and two new diagnoses from samples taken Sunday and Monday, according to city Health Commissioner Dr. Alister Martin. This marks a decrease from earlier daily rates of up to 11 cases.
"All of these things together paint an encouraging sign," Martin said during a virtual news briefing Tuesday. Forty-nine patients have required hospitalization, and 34 have been discharged.
Health officials have inspected all 183 cooling towers in the affected area, with approximately 75 showing positive results in initial tests for Legionella bacteria. These tests do not distinguish between live and dead bacteria. Among the buildings with positive tests is the Metropolitan Museum of Art. The museum is undertaking the required cleanup and follow-up testing, canceling some activities for Wednesday.
Last week, positive tests were also reported at the Guggenheim Museum, several private schools, and apartment buildings. Most of these buildings have completed the mandated cleanup, which involves draining and disinfecting cooling towers. The remaining buildings are expected to complete the process by Thursday.
Legionnaires' disease is a form of pneumonia caused by Legionella bacteria, which thrive in warm water systems like cooling towers, hot tubs, and showerheads. Transmission occurs through inhaling contaminated water droplets, and the disease does not spread from person to person. While treatable, it can be fatal in about 10% of cases, according to the U.S. Centers for Disease Control and Prevention.
Last year, an outbreak in Harlem resulted in seven deaths and over 100 illnesses, with cooling towers at a city-run hospital and the public health lab identified as sources.
The investigation into the current Upper East Side outbreak, first identified on July 2, is ongoing. City officials decided this year to order cleanups before receiving results from second-round tests for live bacteria, a process that typically takes about two weeks, a change from previous protocols.