Infection The bacteria are found naturally in soil and water, and the infection is usually transmitted through water and air.
Legionaires disease is most notorious for infection through air-conditioners especially large plants in hotels and shopping centres.
Legionella bacteria may also be found in hot water tubs.
Symptoms Fever and dry cough, malaise, breathlessness and chest pain.
Diagnosis The inflammation can be seen in a chest X-ray. The bacteria can be found in sputum from the lungs by culture and microscopy, and later anti-bodies can be found in a blood sample.
Treatment Several antibiotics are effective, including ciprofloxacin, azithromycin, erythromycin, tetracyclins and others.
Prevention Avoid hotels with previous outbreaks where the air-conditioning system may be contaminated. Water for showers and baths should be heated to 55C before use, if legionella is suspected.