A sixth person has died in the Upper East Side Legionnaires’ outbreak, which has sickened 90 people since it was first identified in early July, according to the city health department.

“We extend our heartfelt condolences to their loved ones, and our thoughts are with them during this difficult time,” Dr. Alister Martin, the city health commissioner, said in a post on X announcing the death Tuesday evening.

The outbreak of the severe form of pneumonia hospitalized more than 70 people, six of whom remain in the hospital, according to the city health department. But city health officials say no new cases have been diagnosed since July 17 and no new symptoms have been reported in more than two weeks.

“We continue to believe the source of exposure has been eliminated,” Martin said on X.

The city health department says the outbreak is likely linked to a water-cooling tower on the Upper East Side that was contaminated with Legionella bacteria, which can cause Legionnaires' disease when inhaled.

As part of the city’s investigation into the outbreak, the health department has been testing cooling towers for Legionella in three ZIP codes that stretch between Central Park and the East River: 10028, 10128 and 10075.

So far, the city has identified 56 buildings in those ZIP codes whose cooling towers tested positive for live Legionella bacteria. Additional buildings tested positive for Legionella in rapid PCR tests, which identify both live and dead bacteria.

All of those buildings have already been ordered to drain, clean and disinfect their towers in order to rid them of the bacteria. But city health officials say it will take more testing to determine which tower is actually responsible for the outbreak.

Despite city laws requiring the proper maintenance of cooling towers to prevent the growth of Legionella, this is Manhattan's second deadly outbreak of Legionnaires’ disease in two years. A similar outbreak in Harlem last year killed seven.