An outbreak of Legionnaires’ disease in New York City has killed two people and sickened 58 since late July. The disease is a type of pneumonia caused by the bacteria Legionella, which grow in warm water and can spread in building water systems such as showerheads, hot tubs and cooling towers. People can get the disease by inhaling aerosols from contaminated water. Symptoms usually develop two days to two weeks after exposure and include cough, fever, headaches, muscle aches and shortness of breath. Legionnaires' disease can be treated with antibiotics. If untreated, people can suffer complications and even die.