New figures released by New York City's Department of Health and Mental Hygiene on Saturday show four people have now died from the disease and 65 people have contracted it.
The data also says 20 individuals have been successfully treated, and all the people who died were "older adults" and had other underlying medical problems.
If it is caught early, Legionnaires' can be treated. Symptoms include coughing, fatigue and confusion, but the disease cannot spread from person-to-person. Instead, people contract the disease when they breathe in mist or vapor from a contaminated plumbing system.
