What is Legionnaires' Disease?

Legionella pneumophila, is the causative organism for most cases of 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.

How do people get Legionnaires' disease?

Legionnaires' disease does not spread from person to person. The germ which causes Legionnaires’ disease is 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.

Where does Legionnaires' disease come from?

The bacterium which causes Legionnaires' disease is widespread in nature. It mainly lives in water and outbreaks occur from purpose-built water systems where temperatures are warm enough to encourage growth of the bacteria, e.g. in cooling towers, evaporative condensers and whirlpool spas and from water used for domestic purposes in buildings such as hotels, car homes, GP surgeries, dental practices etc.

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 measures are there to control Legionnaires' disease?

To prevent the occurrence of Legionnaires' disease, companies which operate these systems must comply with regulations requiring them to manage, maintain and treat them properly.

More information can be found by HSE ACoP L8 The Control of Legionella Bacteria in Water Systems. Amongst other things, this means that the water must be treated and the system cleaned regularly.

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; and leading on to
  • Pneumonia, very occasionally
  • Diarrhoea and signs of mental confusion.

How is Legionnaires' disease treated?

The illness is treated with an antibiotic called erythromycin or a similar antibiotic.

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