Human infections are caused by inhalation of aerosols containing high numbers of bacteria. Infected people do not transmit the disease to others. Ingestion of the bacteria does not cause infection. Outbreaks of the disease receive significant media attention, but typically only single isolated cases are identified. Symptoms of the disease appear 2 - 10 days following infection.
Initial symptoms are similar to influenza - loss of appetite, tiredness, body aches and headache.
Chills and a rapidly rising fever are usually apparent within 24 hours. Pneumonia develops and kidney function may be affected. Diagnosis of the disease requires identification of the bacteria in the sputum and corresponding antigen levels in the blood or urine. Physicians treat the disease with a prescribed antibiotic regimen. The Legionella bacterium causing this disease is commonly found in the environment in creeks, ponds and soil at excavation sites.