Four people in New York City's Harlem neighbourhood have died from an outbreak of Legionnaires' disease, an aggressive and potentially deadly form of pneumonia. The city has seen 99 confirmed cases with 17 people in hospital with the infection, according to the New York City Department of Health.

A fourth person has died in connection with a Legionnaires’ disease outbreak in New York City. Health officials disclosed the latest death Thursday as they revealed that some cooling towers tested positive for the bacteria in some city-run buildings.

One borough in New York City has been battling a small outbreak of Legionnaires' disease. Here's how to protect yourself if you're traveling to the Big Apple.