Legionnaire's disease and Legionella

Legionnaires' disease is a form of pneumonia or lung infection caused by a bacterium known as legionella pneumophila.

The Causes

The bacterium is widely distributed in nature and is commonly found in surface water and soil.

In the workplace it breeds in warm, moist conditions such as:

  • air conditioning systems
  • fountains and ponds
  • communal showers
  • spa pools  

The risk of catching legionnaires' can be reduced with appropriate maintenance and cleaning of possible sources, such as air conditioning systems.

Infection follows the inhalation of droplets of heavily contaminated water.

It cannot be contracted from another person.

Legionnaire's disease: a brief guide for duty holders (from the HSE UK website)

What are the symptoms?

Symptoms first appear between two and 10 days after exposure to the bacteria. It initially produces a flu-like illness with tiredness, high fever, headache, muscle aches and a dry cough. As the pneumonia develops there may be chest pain, shortness of breath, abdominal pain, vomiting, diarrhoea, and hallucinations.

Who is most vulnerable?

Young people generally make a full recovery, but a proportion of elderly or unfit people die from the illness. 

  • people over 45 years of age
  • smokers and heavy drinkers
  • people suffering from chronic respiratory or kidney disease
  • diabetes, lung and heart disease
  • anyone with an impaired immune system 

Smokers and those with chronic lung disease are especially vulnerable to legionella because the normal defences preventing bacteria entering the lungs are damaged. Occurrences are more common in late summer and early autumn.

More than twice as many men than women are affected and more than two thirds of the cases occur in people over 50.

What is the treatment?

Prompt treatment with antibiotics is effective, but specific types of antibiotic must be used.

Why is it called Legionnaires' disease?

It was named after an outbreak that caused the death of 29 members of the American Legion, the US veteran's society, who were attending a convention in Philadelphia in 1976.

Further information and downloads can be obtained from the Health and Safety Executive UK website