A woman in her 90s has died and six other people have been sickened in an outbreak of Legionnaires’ disease in the Upper East Side of Manhattan, according to New York City health officials. The Department of Health and Mental Hygiene (DOHMH) is investigating the outbreak in the Lenox Hill neighborhood, which runs south to north from East 60th Street to East 77th Street and west to east from Park Avenue to the East River.

Four of the infected are still hospitalized, and two have recovered and been discharged. The elderly woman who passed away had “significant underlying health conditions,” according to the health department.

The DOHMH has been investigating cooling towers (air-conditioning equipment) in the neighborhood, looking for the existence of Legionella bacteria. Cooling towers within a half-mile of the affected area – 116 in total – have been inspected and tested, according to Dr. Mary T. Bassett, the health commissioner. Results of the investigation may take up to two weeks.

A person usually catches Legionnaires’ disease – a serious type of pneumonia caused by Legionella bacteria – by inhaling microscopic water droplets in the form of mist or vapor. Incidents of Legionnaires’ disease typically rise during warmer weather. People at higher risk of getting sick are those 50 years of age or older, current or former smokers, those with a chronic lung disease, and those with a weakened immune system.

People who live in Lenox Hill or travel through the area regularly and are exhibiting pneumonia- or flu-like symptoms – especially anybody displaying those symptoms since the start of June – should seek immediate medical attention.

In 2016, New York reported 718 cases of Legionnaires’ disease, more than any other state.