New York City health officials reported a fifth death linked to a Legionnaires’ disease outbreak, underscoring the seriousness of the bacterial infection and the need to identify its source quickly. The outbreak affected residents in the Bronx, where authorities were investigating buildings and water systems that could have spread contaminated droplets.

Legionnaires’ disease is a severe form of pneumonia caused by Legionella bacteria and is most dangerous for older people, smokers and those with weakened immune systems. Officials urged people with flu-like symptoms, fever, cough or breathing difficulties to seek medical advice, while testing and remediation work continued.