South Bronx Legionnaires' Outbreak Kills One, Sickens Five in NYC's Second Cluster of 2026

One person has died and five others have been diagnosed with Legionnaires' disease in a new cluster centered on the Melrose and Morrisania neighborhoods of the South Bronx, the New York City Health Department announced Thursday night.

The affected area covers ZIP codes 10451 and 10456, according to CBS News. Health officials say results are still pending on additional possible cases.

"Our disease investigators have confirmed five cases of Legionnaires' disease and are working quickly to identify and confirm any additional cases in the area," Health Commissioner Dr. Alister F. Martin said in a statement carried by the New York Post and Gothamist.

Water ecologists have sampled every cooling tower in the affected zone, and those samples are being tested at the city's Public Health Laboratory, according to Archynewsy. Any tower that comes back positive for Legionella will be ordered into immediate cleaning and disinfection, Martin said.

The city will start door-to-door outreach Friday, hold weekend town halls, and run a virtual town hall Sunday at 3 p.m., according to Gothamist and CBS News. Anyone who has lived, worked, or spent time in the area since late August and develops flu-like symptoms, fever, cough, or trouble breathing is being told to see a doctor immediately.

Legionnaires' is a form of pneumonia caused by Legionella bacteria that grows in warm water and spreads through inhaled mist, typically from contaminated cooling towers. It is not contagious between people and responds well to antibiotics when caught early, but it is fatal in roughly 1 in 10 diagnosed cases, according to the CDC as cited by the New York Post.

The Upper East Side outbreak still looms over this one

This is the second Legionnaires' cluster New York City has logged in 2026, following an outbreak on the Upper East Side that started in July, according to Gothamist. That cluster ended up with 94 confirmed cases and 11 deaths, making it the city's deadliest since a 2015 outbreak in the Bronx killed 17, Gothamist reported. The Post put the hospitalization count at nearly 80.

Martin said that cluster is no longer spreading and that none of its patients remain hospitalized. But the city's initial handling of it drew criticism, according to the New York Post, which reported the Mamdani administration faced backlash over a slow response and delays in pinning down the source. No agency has publicly identified the exact origin of the Upper East Side cluster to date.

Days before the South Bronx cluster surfaced, the city confirmed a cooling tower atop the NYPD's 112th Precinct in Queens tested positive for trace amounts of Legionella. Officials classified the reading as Level 2, low enough that state law doesn't require notifying people who use the building, sources told the Post. The department said no confirmed Legionnaires' patient has reported working at that precinct.

A pattern that predates this year

This is not the first time the city has faced a serious Legionella cluster. A 2025 outbreak in Central Harlem killed people and hospitalized dozens, though the exact toll is reported inconsistently. The New York Post put it at seven deaths, 114 cases and 90 hospitalizations. The Harlem Legionnaires Task Force, a community group formed after that outbreak, cites eight fatalities, 117 cases and 90 hospitalizations. Neither figure has been reconciled in these sources, and readers should treat both as reported rather than confirmed against a single authoritative count. Municipal data cited by Archynewsy also notes that multiple community clusters occurring in the same calendar year previously happened in 2015, 2016, 2017 and 2018.

Families of Harlem victims filed lawsuits against the city in August, including a wrongful-death claim tied to five of the deceased, the Post reported. Those suits are pending; no city liability has been established in court.

Gov. Kathy Hochul signed legislation in August tightening inspection requirements for New York City cooling towers, and city officials separately said this month they want to expand oversight further, according to CBS News. Building owners are already required to register cooling towers and conduct routine Legionella testing, with records kept in a city database that investigators use to trace outbreaks, Archynewsy reported.

The concern from residents and some council members, reflected across this year's cluster of clusters, is straightforward: if registration and testing requirements were already on the books before the Harlem and Upper East Side outbreaks, why do these events keep recurring. The city's counter is equally straightforward: officials point to faster action this time, samples were pulled from every tower in the affected zone within days, and outreach began the next morning, a noticeably quicker cadence than the criticized Upper East Side response.

Whether that faster process traces the South Bronx source before more people get sick is the open question. The city has not said when results on pending cases or tower samples will be finalized, and no cause for the current cluster has been identified as of Thursday night's briefing.