A Legionnaires' disease outbreak in New York's Central Harlem neighborhood has now sickened 90 people and caused three deaths, health officials said Tuesday.

New York City health officials are continuing to investigate a cluster of Legionnaires’ disease, a serious bacterial lung infection, where the number of cases has risen to 73, including three deaths.

A Legionnaires' disease cluster in the Harlem area of New York City has caused three deaths and 90 people to be sickened. Here's what it is, symptoms and how it's spread.