Legionnaires' Disease

The condition known as Legionnaires' disease was named after an outbreak of a severe pneumonia-like disease that occurred at the Belle Vue Stratford Hotel, Philadelphia, USA in 1976, where there was a convention of the American Legion.

Legionella pneumophila, the causative organism for most cases of Legionnaires' disease, was thought to have been present in the hotel’s cooling towers.

Somehow, water droplets in the form of an aerosol contaminated the hotel's air conditioning systems allowing the bacteria to come into contact with the convention guests, a highly susceptible population.

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.

Check out our infographic describing the disease in a quick and easy to understand wayCheck out our infographic describing the disease in a quick and easy to understand way

How do people get it?

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.

Legionnaires' disease does not spread from person to person.

Where does it come from?

The bacterium that 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, e.g. in cooling towers, evaporative condensers and whirlpool spas (tradename Jaccuzi) and from water used for domestic purposes in buildings such as hotels.

Most community outbreaks in the United Kingdom 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 that operate these water systems must comply with regulations requiring them to manage, maintain and treat them properly.

Amongst other things, this means that the water used in the systems must be treated correctly 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 it treated?

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

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 (usually a urine-antigen 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.

In the UK 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.

Legionnaires' risk assessment

More about Legionnaires' disease

For more information about this condition including transmission, epidemiology, diagnosis, treatment and prognosis... Legionnaires' disease

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