NYC Health Officials Confirm Legionnaires’ Outbreak Linked to Cooling Towers, Launch Aggressive Testing and Disinfection Drive

Justine Kirby has begun wearing an N95 mask each time she steps out in her Upper East Side neighbourhood and keeps her apartment windows shut. The city now counts 46 cases of Legionnaires’ disease, all tied to contaminated cooling towers.

She keeps her apartment windows closed, while an outbreak of Legionnaires’ disease has risen to 46 cases, all linked by the city to contaminated cooling towers.

The surge in Legionnaires’ infections – a severe pneumonia caused by Legionella bacteria – has sparked community alarm. Residents filled a church hall on the Upper East Side this week to question New York City’s health department.

“There is a great deal of concern in the community,” Kirby commented. “I think the risk might be low, but until cleaning and disinfection are completed, there’s little downside to taking these precautions.”

As of Wednesday evening, health officials reported that 22 infected individuals had been hospitalized, with some requiring intensive‑care treatment.

Legionnaires’ disease is caused by Legionella bacteria that thrive in warm water. The infection produces flu‑like symptoms and can be fatal if untreated, especially among immunocompromised individuals.

The outbreak originates from cooling towers on larger buildings, where Legionella bacteria flourish and become airborne when inhaled as mist, according to Dr. Wafaa El‑Sadr, an epidemiology professor at Columbia University’s Mailman School of Public Health.

The city unveiled an aggressive response plan this week. Mayor Zohran Mamdani announced on Friday that officials had tested every cooling tower in the affected area.

Health Commissioner Alister Martin reported that Legionella was found in 31 towers, with 19 already disinfected. The remaining buildings were slated to complete cleaning by Saturday, according to CBS News, a BBC US partner.

Cooling towers are integral components of large air‑conditioning and refrigeration systems, cooling indoor spaces by venting heat through water evaporation that creates mist, per the NYC health department. They typically sit atop buildings.

Officials now mandate immediate full cleaning and disinfection of any tower that tests positive, rather than awaiting confirmatory samples.

Speaking at the church town hall, Commissioner Martin highlighted the positive news that the city had detected the outbreak early.

“We are monitoring 160 cooling towers across the region, and we are acting now,” he said, according to ABC Newsexternal.

Council Speaker Julie Menin expressed concern that insufficient action had been taken.

In a letter to Commissioner Martin, she wrote that she was deeply concerned “that the Department of Health and Mental Hygiene has still failed to require building owners to proactively disinfect all cooling towers under investigation.”

Kirby said she found comfort in the health department’s testing efforts but noted that she and many of the dozens of attendees still had unanswered questions about personal protection.

The city advises residents to monitor for symptoms and seek medical care, including testing, if they become ill.

Kirby commented, “It would be reasonable to say that while the risk is low, a well‑fitted mask can still protect you. I wish they had addressed that.”

The health department did not reply to a BBC inquiry about mask guidance, though Dr. El‑Sadr noted that masking and keeping windows closed could help those in the outbreak’s epicentre.

Dr. El‑Sadr warned that rising temperatures due to climate change could exacerbate Legionnaires’ outbreaks, although the disease has affected New York and other major cities worldwide for many years.

London, Ontario, reported 105 Legionnaires’ cases and five deaths in 2025. Last August, Harlem in Upper Manhattan saw 114 infections and seven fatalities, later traced to cooling towers at Harlem Hospital and the nearby public health laboratory.

The Upper East Side contains far more cooling towers than were tested during the 2025 Harlem outbreak—over three times the number—according to the NYC Department of Health and Mental Hygiene.

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