NYC Legionnaires Disease Cluster Slows as Cooling Tower Remediation Continues

Yesterday, the number of newly infected patients with Legionnaires disease—related to the recent Legionnaires disease cluster plaguing the Upper East Side of Manhattan, New York—appeared to be waning.¹

The most recent report from the New York City Health Department cited 1 newly infected patient as of July 12, a significant decrease from the 11 new cases reported at the peak of the cluster surge on July 6.¹ As of July 13, there are a total of 60 cases of Legionnaires disease, 15 of whom are currently hospitalized, and no reported deaths. The city’s health department identified 31 buildings that tested positive for Legionella bacteria. More than half have complied with the health department’s order to clean and disinfect their cooling towers by July 11, according to the most recent update.² The health department’s press release also affirmed the outbreak is not related to the plumbing systems in any of the buildings listed and assured residents that the tap water is safe to continue using.¹

Community cluster infections of Legionnaires disease have been attributed to exposure from cooling towers, hot tubs, and spray fountains, according to the city’s health department’s recent press release. During a virtual town hall addressing the community cluster, Celia Quinn, a career epidemiology field officer from the CDC, explained that PCR, or molecular screening, for Legionella bacteria cannot confirm or deny whether the bacteria are alive. ³

Nonetheless, it’s in the health departments’ and the public’s best interest that they take immediate action by “ordering the cooling tower operators to remediate.” Yet, “There’s no difference in the risk of getting Legionnaires’ disease from being in or near a building that tested PCR positive versus the rest of the zip codes,” Quinn said.³

The NYC Health Department and the mayor’s administrative office are taking swift action to address and quell the community cluster of Legionnaires disease. This is not an uncommon predicament, as the health department cites approximately 300 to 700 reported cases of the disease each year.¹

What distinguishes this occurrence of Legionnaires disease is that the size of the community cluster is uncommon. And it’s large enough to require an investigation, public sampling, and immediate remediation.

“There are different kinds of patterns that we see. When we see a pattern of cases in the same building or at the same address where people share a hot water system, and there are cases that might happen over a 12-month period, that leads us to think it could be growing in the building's internal plumbing system,” Corinne Schiff, JD, deputy commissioner for environmental health, said during the virtual town hall. “That's not what we have here. The pattern that we see here is…cases in a tighter time frame in a neighborhood…that’s called a community cluster.”

Another High-Profile US Legionnaires' Disease Investigation in 2026

The Upper East Side investigation, concentrated in the neighborhoods of Carnegie Hill and Yorkville, is not the first to garner public attention this year. In May, 18 cases of Legionnaires disease were linked to an outbreak at Kaiser Santa Clara Medical Center in Santa Clara, CA.⁴ Both incidents underscore the importance of vigilant maintenance of both cooling towers and complex building water systems, in addition to rapid public oversight when clusters emerge.⁴

“We’re using every tool available to protect people by moving quickly to identify potential sources of exposure, requiring immediate remediation, and making sure New Yorkers have the information they need to keep themselves and their families safe,” Mayor Zohran Kwame Mamdani said in a press release.

References

1. Legionnaires’ disease. NYC Health . July 13, 2026. Accessed July 14, 2026. https://www.nyc.gov/site/doh/health/health-topics/legionnaires-disease.page

2. NYC Health Dept. releases preliminary list of buildings ordered to clean and disinfect their cooling towers. NYC Health. July 10, 2026. Accessed July 14, 2026. https://www.nyc.gov/site/doh/about/press/pr2026/preliminary-list-clean-disinfect-cooling-towers-legionnaires.page

3. NYC Health. Legionnaires Disease Virtual Town Hall | July 13, 2026. YouTube. Published July 14, 2026. Accessed July 14, 2026. https://www.youtube.com/watch?v=RNmHZMQaai0

4. McCrear S. Legionella outbreak linked to Kaiser Santa Clara infects 18 in California. AJMC^®. May 12, 2026. Accessed July 14, 2026. https://www.ajmc.com/view/legionella-outbreak-linked-to-kaiser-santa-clara-infects-18-in-california