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.

The health department offered five ZIP codes in central Harlem -- 10027, 10030, 10035, 10037, 10039 – that were at the center of the cluster, as officials stressed the disease was airborne and could reach people even outside of the directly affected buildings.

The last of 12 cooling towers that tested positive for the bacteria currently spawning a Legionnaires’ outbreak in Harlem is being remediated Friday, with officials hoping containment efforts will help prevent another death.