Three people in central Harlem have already died from legionnaires’ disease, according to the NYC Health Department.

There have now been 90 confirmed cases of legionnaires’ disease in central Harlem, and 15 people are currently hospitalized battling the disease, the city’s health department announced this week.

What are the symptoms of this type of pneumonia, called Legionnaires' disease, and how do you treat it? Here's what you need ...