NYC Health Department Declares Upper East Side Legionnaires’ Disease Cluster Exposure Has Ended
No New Symptoms of Legionnaires’ Disease Related to This Cluster in Two Weeks, Confirming Exposure Source Was Eliminated Early
Transparency and Aggressive Enforcement Increase Compliance With New Monthly Cooling Tower Testing Law to 97%
July 31, 2026 — Today, the New York City Health Department announced that the incubation period for new cases has passed and there is no longer an elevated risk of exposure in ZIP codes 10028, 10075, and 10128 on the Upper East Side.
The last day that anyone who lives, works, or visited the area began feeling symptoms of Legionnaires’ disease was two weeks ago. Legionnaires’ disease has an incubation period of two to 14 days after exposure.
As a result of the Health Department’s aggressive response to this cluster — which included ordering all cooling towers with initial positive screening to be fully drained, cleaned, and disinfected — the source of exposure has been eliminated.
More than 90% of patients developed symptoms before July 7, just five days after the Health Department launched its investigation and ordered buildings with positive screening tests to remediate their cooling towers.
The Health Department continues to investigate the source of exposure to the Legionella bacteria associated with this cluster. As of July 30, there have been 92 cases of Legionnaires’ disease associated with the cluster; 79 people have been hospitalized; five remain hospitalized; and, unfortunately, seven people have died.
“All New Yorkers deserve a government that responds quickly, acts transparently, and never hesitates to protect public health,” said NYC Health Commissioner Dr. Alister F. Martin. “The moment we identified a potential community cluster, we mobilized more than 260 Health Department staff, tested every cooling tower in the affected area, and directed every building with an initial positive test to immediately clean and disinfect its cooling tower, before we ever confirmed live Legionella bacteria were present. We continue to enforce New York City’s rigorous cooling tower regulations and hold accountable any building owner who fails to meet their responsibility to keep New Yorkers safe.”
More than 260 Health Department staff members supported the response, interviewing and reviewing records for more than 150 potential cases, collecting samples from more than 180 cooling towers, and performing more than 360 different tests on the samples. Staff also distributed over 6,000 informational flyers and palm cards in three languages, hosted a webinar for healthcare providers, held multiple public briefings and town halls, issued nine public updates, and provided daily updates on nyc.gov/legionnaires and social media.
The Health Department ultimately ordered 83 buildings to clean and disinfect their cooling towers. Every building complied. Fifty-nine cooling towers tested positive for live Legionella bacteria, while 124 tested negative.
Inspections Identify Two Cooling Towers With Significant Maintenance Failures
The Health Department has completed inspections for all 82 cooling towers under their jurisdiction that tested positive for Legionella through PCR screening or confirmatory culture testing. Inspectors reviewed maintenance records, operating procedures, and compliance with the City’s new law requiring monthly Legionella testing and reporting.
Sixty percent of inspections resulted in at least one violation, totaling more than 110 violations, including more than 15 public health hazards, more than 50 critical violations, and more than 40 general violations.
The cooling tower with the most violations is located at 300 E. 83rd St. This cooling tower was unregistered, and the Health Department investigators identified it by comparing Department of Buildings construction permit records with cooling tower registration data and conducting targeted inspections of potentially unregistered cooling towers.
The unregistered cooling tower was operating illegally because it had never been registered with the City. Inspectors found that the owners had failed to develop a required maintenance program and plan, document water treatment, or conduct any Legionella sampling for more than a year. The Health Department cited 11 violations and has issued $11,000 in fines to the building owners to date.
The cooling tower with the second-highest number of violations is located at 1520 York Ave. Inspectors cited nine violations and have issued $9,000 in fines to date, including failure to develop a required maintenance program and plan, document water treatment, and conduct the newly required monthly Legionella sampling.
Transparency Increased Compliance With New Monthly Testing Law
On July 10, the Health Department publicly released a preliminary list of buildings whose cooling towers had tested positive by PCR for the presence of Legionella bacteria, providing a level of transparency not previously offered during a community cluster Legionnaires’ disease investigation.
As additional lab results became available, the Health Department updated the public list, including buildings whose cooling towers later tested positive through culture testing. This unprecedented transparency drove improved compliance.
On July 11, one day after the preliminary list was released, 74% of the 82 cooling towers for which the Health Department has completed inspection had submitted records demonstrating compliance with the City’s new monthly testing requirement. By July 24, compliance had increased to 97%. Among all 183 cooling towers sampled in the affected area, compliance increased from 73% to 92%. Citywide, compliance increased from 77% to 80%. Cooling towers that have not reported may not be subject to the requirement at this time because they were not operating during the applicable reporting period.
Genome Sequencing
The Health Department’s Public Health Laboratory is comparing bacterial samples from patients with samples recovered from cooling towers that tested positive for live Legionella bacteria. Results from the sequencing analysis are expected by the end of August.
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MEDIA CONTACT: PressOffice@health.nyc.gov