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Legionnaires' disease

What is it?

Legionnaires' disease is caused by the legionella pneumophila bacterium and is a type of pneumonia. The bacteria is found in fresh water, warm water environments, cooling towers, hot water systems, whirlpool spa baths, clinical humidifiers in respiratory equipment, supermarket vegetable sprays, natural spa baths, fountains, soil and potting compost. Most of the major outbreaks are associated with cooling towers and large water systems. The legionella bacteria can also cause other flu like diseases such as Pontiac fever and Lochgoilhead fever.

How is it caught and what happens?

Legionnaires' disease can break out if a pathogenic strain of legionella is introduced into the water system, either through contaminated water or contaminated aerosolised water droplets. It is widely accepted that Legionnaires' disease is contracted through inhalation of water droplets infected with the legionella bacterium. Legionnaires' disease does not spread directly from one person to another. However, reports suggest that rarely the bacteria can be aspirated when drinking heavily contaminated water and accidentally inhaling it. Therefore it is essential to maintain a microbiological count of less than (103) - (104). It has also been recorded that on other rare occasions, Legionella counts have been detected within 35 minutes within the mouth of humans who have consumed drinking water. The illness has a low infection rate (around 5%) but a death rate of around 12% (in reported cases), so although risk of infection is quite low, once you display symptoms you must seek medical assistance immediately.

Legionnaires' disease has an incubation period of around 2 - 10 days. Symptoms include loss of energy, high fever, dry cough, aching muscles, headache, chest pains and shortness of breath. As the infection develops it attacks other parts of the chest cavity and most of the body's systems including the abdominal region and the brain. Nausea and diarrhoea can also afflict those infected. If found quickly, Legionnaires' disease is curable, however the disease can kill and those who survive may suffer permanent physical or mental impairment. If you suspect Legionnaires' disease you must see your doctor or go to a local hospital immediately. The illness can be treated by various antibiotics when caught in the early stages.

Further Information

For more inforamtion about Legionnaires' disease and to download the relevant ACOP guidance documents visit