Legionellosis causes

Overview
The bacteria that cause Legionnaire's disease have been found in water delivery systems. They can survive in the warm, moist, air conditioning systems of large buildings, including hospitals. Most cases are caused by Legionella pneumophila. The rest of the cases are caused by other Legionella species.Spread of the bacteria from person to person has not been proven. Most infections occur in middle-aged or older people, although they have been reported in children. Typically, the disease is less severe in children.