Legionella bacteria are widely distributed in the environment. They have been found in creeks and ponds, hot and cold water taps, hot water tanks, water used in air conditioning cooling towers and evaporative condensers, and soil at excavation sites. The disease appears to be spread through the air from a soil, or a water source. Patients have ranged in age from 10 months to 84 years, however, the majority of the cases occurring after the age of 50. The disease most often affects middle-aged, or older men, particularly those who either smoke, or drink heavily.
Males contract the disease nearly two and a half times more often than females.
People with underlying illnesses such as cancer, or those with lowered immune system resistance to disease are also at higher risk. The early symptoms of legionellosis may be flu-like with muscle aches, headache, tiredness and dry cough followed by high fever, chills and occasionally diarrhea. Temperatures commonly reach 102- 105 o F, and subsequent chest radiographs often reveal pneumonia. Antibiotics such as erythromycin appear to be effective in treating the disease. Legionellosis often causes symptoms similar to those caused by influenza virus and other types of bacterial pneumonia.