The city health department has launched an investigation after a cluster of Legionnaire’s disease cases were identified in Harlem over the weekend — with officials urging New Yorkers to take precautions.

Five cases of the potentially fatal pneumonia-like illness were diagnosed in the Manhattan neighborhood in recent days, although no deaths have been reported, the department said.

“Any New Yorkers with flu-like symptoms should contact a health care provider as soon as possible,” deputy chief medical officer Dr. Toni Eyssallenne said in a statement.

“Legionnaire’s disease can be effectively treated if diagnosed early,” Eyssallenne said. “But New Yorkers at higher risk, like adults aged 50 and older, those who smoke or have chronic lung conditions should be especially mindful of their symptoms and seek care as soon as symptoms begin.”

Although potentially lethal if not treated in time, Legionnaire’s disease is not contagious and can be treated with antibiotics, the department said.

The disease is typically transferred through water supplies contaminated with Legionella bacteria that can pop up in plumbing systems, and can find favorable conditions in cooling towers, whirlpool spas, hot tubs, humidifiers and condensers in large air conditioning systems, health officials said.

Last month, officials in Sydney, Australia, reported a death from a Legionnaire’s case there.

In October, a dozen cruise ship passengers were diagnosed with the disease in two cases, including 10 who had to be hospitalized, while another outbreak was reported at two Las Vegas casinos in 2023.

In 2022, at least two dozen people in the Highbridge section of the Bronx were diagnosed with Legionnaire’s, with two dying and others hospitalized with the disease.

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