New York City health officials have confirmed that one person has died of complications related to Legionnaires' disease in a cluster of 18 cases in one Manhattan neighborhood.

The city Health Department said Tuesday that the victim is a person over the age of 50.

Nine people were hospitalized and released, and seven were still in the hospital, due to the outbreak in the lower Washington Heights area, officials said in the afternoon.

The health department said the last reported infection was July 11.

City officials warn New Yorkers to be vigilant if they live in lower Washington Heights or northern Hamilton Heights, as someone may have been infected last week and has not felt symptoms yet because of the disease's two-week incubation period.

Health officials said they have inspected 20 cooling towers and ordered several building owners to increase their use of biocides to kill the bacteria associated with the disease.

Legionnaires' is a form of pneumonia contracted by breathing in water droplets contaminated with the bacterium Legionella. Most cases can be traced to plumbing systems where conditions are favorable for Legionella growth.

Adults who experience flu-like symptoms, fever, cough, or difficulty breathing should seek medical attention immediately.

The disease is not contagious and is easily treatable when caught early.

The city sees an average of 200 to 500 Legionnaires' cases each year.