A growing cluster of Legionnaires' disease cases on Manhattan's Upper East Side has reached 54 confirmed infections, including 18 hospitalizations, according to city health officials.

The New York City Health Department said the cases have been identified in the ZIP codes 10028, 10128 and 10075. No deaths have been reported.

Officials said people who live, work or have visited those areas since late June should monitor for symptoms and seek medical care if they become ill.

Legionnaires’ disease is a type of pneumonia caused by Legionella bacteria that thrive in warm water. Symptoms include cough, fever, muscle aches and difficulty breathing.

The Health Department said that the investigation is not related to any building's plumbing system. Residents can continue to safely drink tap water, bathe, shower, cook and use air conditioning in their homes.

The disease is not contagious and cannot be spread from person to person.

Those at greatest risk include adults age 50 and older, people who smoke or vape, those with chronic lung disease, weakened immune systems or people taking medications that suppress the immune system, according to the department.

The agency believes the source of the bacteria is likely a cooling tower in the affected area. It is testing cooling towers throughout the affected area.

The cluster follows a Legionnaires' disease outbreak in Central Harlem last summer that sickened more than 100 people and killed seven.