A Legionnaires’ disease outbreak on Manhattan’s Upper East Side has grown to 14 confirmed cases, New York City health officials said Sunday.

The cases are tied to ZIP codes 10028, 10128 and 10075, covering parts of the Upper East Side, including Yorkville and Carnegie Hill. At least one patient lives, works or recently visited the 10075 area, health officials said.

Officials are also urging anyone who spent time along the east side of Central Park between East 76th Street and East 97th Street to watch for flu-like symptoms, including fever, cough, chills and muscle aches.

MYSTERY PARASITE LEAVES AMERICANS BATTLING ‘EXPLOSIVE’ ILLNESS AS CDC INVESTIGATES

“I want to acknowledge the NYC Health Department’s staff of epidemiologists, water ecologists, community health workers, and many more who spent the last few days working to keep New Yorkers on the Upper East Side informed and safe,” NYC Health Commissioner Dr. Alister F. Martin said in a statement.

Legionnaires’ disease is a severe form of pneumonia caused by Legionella bacteria. People can become infected by breathing in contaminated water droplets, and the illness can be dangerous — even deadly — without quick treatment.

WEST NILE VIRUS DETECTED IN SOUTHERN STATE AS HEALTH OFFICIALS WARN RESIDENTS ABOUT MOSQUITOES

The source of the outbreak remains under investigation. Officials say they are testing cooling towers in the affected area as a possible source, though no specific source has been identified.

Cooling towers, often found on rooftops, can release mist carrying Legionella bacteria. The Health Department said all cooling towers in the affected area are being tested.

The cluster was first announced Thursday, when only two cases had been confirmed. The area of investigation has since expanded as more illnesses were reported.

RARE TICK-BORNE VIRUS TURNS DEADLY FAST AS US CASES REACH RECORD HIGH, EXPERTS WARN

“We identified the cluster early when there were just two confirmed cases, and we’ve acted swiftly and decisively, setting holiday plans aside to step up for our fellow New Yorkers. There is more work to do in the days ahead as we learn more about the source of exposure and confirmed cases,” Martin said. 

New York City Mayor Zohran Mamdani said the outbreak is not tied to building plumbing or indoor air conditioning units, and residents in the area can safely drink tap water, bathe, shower, cook and use their AC at home.

Officials said they will continue providing updates as more information becomes available.

“Please contact a health care provider immediately if you live, work or visited the area since late June and are experiencing flu-like symptoms, such as cough, fever or difficulty breathing,” Mamdani wrote on X.

Last summer, a Legionnaires’ disease outbreak in Central Harlem led to more than 100 confirmed illnesses, according to FOX 5.