Legionnaires’ disease is a rare condition, and incidence is hard to estimate because diagnosis requires a suspicion of disease and ordering of the tests needed for confirmation, said Krishna Thavarajah, MD, a pulmonologist and director of the Interstitial Lung Disease Program at Henry Ford Hospital, Detroit, in an interview.

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

Harlem Hospital is one of several locations where people were exposed to Legionnaires’ disease since the outbreak in Central Harlem, officials said Thursday. The spread began in Central Harlem on July 25 with five reported cases of the disease.