Legionnaires' disease

Legionnaires’ disease is a serious lung infection caused by legionella bacteria.

Initial symptoms include a high fever, muscle pain and chills. Once bacteria infect your lungs, you may also develop a persistent cough, chest pains and breathing difficulties.

You should see your GP if you develop any of the initial symptoms, as they are likely to mean you have an infection of some kind. 

If you have serious problems like chest pains and breathing difficulties, seek urgent medical attention.

As the condition has similar symptoms to other illnesses, recent places you have visited will help in making a diagnosis. If it is suspected you have an infection, a urine test can check for Legionnaires' disease. 

Read more about symptoms of Legionnaires' disease and diagnosing Legionnaires' disease.

How does Legionnaires’ disease spread?

Legionnaires’ disease is the result of legionella bacteria infecting your lungs.

It is usually caught by breathing in small droplets of contaminated water. It is not contagious and cannot be spread directly from person to person.

Legionella bacteria is commonly found (often in harmlessly low numbers) in sources of water, such as rivers and lakes. However, the bacteria can rapidly multiply if they find their way into artificial water supply systems such as air conditioning systems.

Large buildings, such as hotels, hospitals, museums and office blocks, are more vulnerable to legionella contamination because they have larger, more complex water supply systems in which the bacteria can quickly spread.

Read more about the causes of Legionnaires’ disease.

Treating Legionnaires' disease

Legionnaires' disease is treated with a course of antibiotics either taken orally, such as a pill, or through a continuous drip into a vein in your arm.

The length of time you need antibiotic treatment for will depend on the severity of the condition. Treatment usually lasts around a week, but may continue for up to three weeks.

As Legionnaires' disease can be particularly serious in people with pre-existing health conditions, you may be admitted to hospital for a few weeks so your health can be monitored.

Read more about treating Legionnaires’ disease.


Most people make a full recovery from Legionnaires' disease. However, in some cases it can lead to further, life-threatening, problems.

For example, the disease may cause some of your organs, such as your lungs or kidneys to stop working properly. Another complication is septic shock, which is the result of a blood infection causing a sudden drop in blood pressure.

An estimated 10-15% of otherwise healthy people who contract Legionnaires’ disease will die due to problems like these. In 2010, there were 38 deaths from Legionnaires’ disease in England and Wales.

Can Legionnaires' disease be prevented?

The best way to prevent an outbreak of Legionnaires’ disease is to ensure any water system under your control is properly maintained and conforms to relevant health and safety regulations.

This mainly involves keeping water either cooled below 20ºC or heated above 60ºC. The water supply should also be kept free of any impurities and kept moving so it doesn't stagnate.

Read more about preventing Legionnaires' disease.

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