. A 60-year-old man is diagnosed to be suffering from Legionnaires' disease after attending a conference. How did he acquire it?

He most likely acquired it from inhalation of aerosol in the air-conditioned room at the conference due to cooling towers. Legionella can be found in natural, freshwater environments, but generally is not present in sufficient numbers to cause disease. Infection is typically by inhalation of aerosols produced by cooling towers, air conditioners and shower heads which act as disseminators No animal reservoirs exists, no human to human transmission occurs, and no carrier state is established. Reference: Ananthanarayan and Paniker&;s Textbook of Microbiology Tenth edition