A fifth person has died in New York City amid an ongoing cluster of Legionnaires' disease on the city's Upper East Side neighborhood, according to health officials.

At least 82 cases have been identified and eight people remain hospitalized as of Tuesday, the New York City Health Department said.

Since the cluster began, 56 people have been discharged from the hospital, according to the department.

Legionnaires' disease is a form of severe pneumonia caused by a type of bacteria that thrives in warm, stagnant water. Health officials have focused on testing cooling towers that are part of air conditioning systems for large buildings. Property owners have been ordered to drain and disinfect towers where there has been a positive test result.

So far, 34 cooling towers at 33 buildings that had live bacteria have been cleaned and disinfected, health officials said on Tuesday. Nine towers tested negative for the bacteria, and the test results from the remaining 140 towers are expected over the next week, they said.

Legionnaires' disease is treatable, but about 10% of patients die from complications, according to the US Centers for Disease Control and Prevention.

The outbreak comes less than a year after another cluster in New York City's Harlem neighborhood sickened more than 100 people and claimed seven lives.