What is legionnaires' disease?

Legionnaires' disease is a type of pneumonia. It was named after an outbreak of severe pneumonia which affected a meeting of the American Legion in 1976. It is an uncommon but serious disease.

The illness occurs more frequently in men than women. It usually affects middle-aged or elderly people and it more commonly affects smokers or people with other chest problems. Legionnaires' disease is uncommon in younger people and is very uncommon under the age of 20.

About half the cases of legionnaires' disease are caught abroad. The other half are the result of infections acquired in the UK.

How do people get it?

Legionnaires' disease is cause by a bacterium called Legionella pneumophila. People catch legionnaires' disease by inhaling small droplets of water suspended in the air which contain the Legionella bacterium. However, most people who are exposed to Legionella do not become ill.

Legionnaires' disease cannot spread from person to person.

Where does it come from?

The bacterium which causes legionnaires' disease is widespread in nature. It mainly lives in water, for example ponds, where it does not usually cause problems. Outbreaks occur from purpose-built water systems where temperatures are warm enough to encourage growth of the bacteria, eg in cooling towers, evaporative condensers, whirlpool spas and from water used for domestic purposes in buildings such as hotels.

Most community outbreaks in the UK have been linked to installations such as cooling towers or evaporative condensers which can spread droplets of water over a wide area. These are found as part of air-conditioning and industrial cooling systems.

What are the symptoms?

The symptoms of legionnaires' disease are similar to the symptoms of the flu:

• high temperature, feverishness and chills
• cough
• muscle pains
• headache
• pneumonia
• diarrhoea
• signs of mental confusion

How is it treated?

The illness can be successfully treated with antibiotics such as erythromycin.

What to do

If you develop the above symptoms and you are worried that it might be legionnaires' disease, see your general practitioner.

Because it is similar to the flu, it is not always easy to diagnose. A blood or urine test will be helpful in deciding whether an illness is or is not legionnaires' disease. When doctors are aware that the illness is present in the local community, they have a much better chance of diagnosing it earlier.

If you suspect that you may have got the illness as a consequence of your work then you are advised to report this to your manager, as well as your health and safety representative and occupational health department, if you have one. There is a legal requirement for employers to report cases of legionnaires' disease that may be acquired at their premises to the Health and Safety Executive

Back to top