As of July 6, 23 cases of Legionnaires' disease have been confirmed in two of Manhattan's Upper East Side neighborhoods, according to the New York City Department of Health. There have been 17 hospitalizations, but so far, no deaths have been associated with the cluster.
In a notice to the two neighborhoods -- Carnegie Hill and Yorkville -- the department said it believes the likely source of the bacteria is a cooling tower in the area, which sprays a mist that contains the bacteria.
The health department said there is no issue with any building's plumbing system and that residents in the affected areas can continue to drink tap water, bathe, shower, cook and use their air conditioners.
Residents say it's something they're thinking about. -- the misty bacteria lingering in the air over parts of the Upper East Side that's caused several people to become critically ill.
New York City health commissioner Dr. Alister Martin spoke with Eyewitness News on Monday.
Martin said there are a number of patients who are critical and in the ICU.
The outbreak was detected late last week in Yorkville and Carnegie Hill -- a single square mile area from East 74th to East 96th streets. The patients live in the ZIP codes 10028, 10128, and 10075.
The precise source is still not clear. Legionella bacteria cause a potentially fatal form of pneumonia.
A similar outbreak in Harlem last year killed seven people and sickened 114 others.
Although most people recover from Legionnaires' disease with antibiotics, certain patients -- including those who are immunocompromised or who suffer from chronic lung diseases -- can develop complications that can be fatal.
About one out of every 10 people who develop Legionnaires' disease will die due to complications, according to the CDC. Among those who develop Legionnaires' disease during a stay in a healthcare facility, about one out of every four people will die, the federal health agency added.
The NYC health department said anyone who lives or works in the affected areas -- or has visited since late June -- and is experiencing flu-like symptoms should contact a healthcare provider immediately.
(ABC News contributed to this report.)
----------
* Get Eyewitness News Delivered
* More New York City news
* Send us a news tip
* Download the abc7NY app for breaking news alerts
* Download our connected TV app