What is Legionnaires' Disease?

By: Alex Winter on Sep 6, 2019

Legionnaires' disease is a serious form of pneumonia which infects the lungs.

How serious is it?

The disease is a severe, and even potentially fatal disease and is especially dangerous to groups who are at greater risk:

  • People suffering from chronic respiratory or kidney disease
  • People who suffer from diabetes, lung and heart disease
  • Anyone with an impaired immune system
  • Those who are over 45 years of age
  • Anyone who smokes or is a heavy drinker

(It is rare for babies or children to catch the disease).

What causes it?

A bacterium called Legionella pneumophila which lives in natural water sources such as lakes, reservoirs, rivers and streams. It can also be found in man-made water systems such as hot and cold water systems, cooling towers and spas. 

Where would you catch it?

Man-made environments can contain the perfect conditions for the Legionella bacterium to multiply and may produce the water droplets that carry the bacterium.

These generally tend to be found in industrial or commercial premises – it is rare that Legionnaires' disease is caught in the home.

How do you catch it?

You can catch Legionnaires' disease by inhaling water droplets containing the Legionella bacterium. These water droplets can then make their way into the lungs via aspiration, which then become infected.

Is it infectious?

No. People who are infected cannot transmit the disease. There are no special precautions that need to be taken around someone with the disease.

Can it be treated?

If it is caught in the early stages and treated, a healthy patient should make a full recovery. Patients with existing health issues that affect the respiratory system or compromise the immune system may suffer prolonged hospitalisation, complications or even, in the worst cases, death. Treatment is usually in the form of antibiotics.

What are the symptoms?

Symptoms will appear between two to ten days after contracting the disease. As the disease is a form of pneumonia, it can feel like severe flu. Symptoms may include a high fever, chills, cough, muscle aches, headaches, and diarrhoea.

What are the long-term effects?

If treatment proved effective, then patients may suffer no long-term effects, if not, then they may suffer a range of on-going issues such as fatigue, neurological damage or neuromuscular damage.

What precautions can I take against catching the disease?

The best way for someone who is otherwise in good health to prevent themselves from getting Legionnaires' is to avoid smoking.

If you are in an at-risk group, you should boil water when travelling – this will kill any bacteria present in the water.

Although infections in people’s homes are rare – here is a list of precautions you can take:

  • Make sure your boiler or hot water tank is working properly and keep it well maintained.
  • Keep the temperature settings on your boiler or hot water system set to heat up to 60 degrees Celsius. However, this temperature could scald causing injury, so only do this where you have mixer taps with a thermostatic mixing valve. Do not do this where elderly people and children may be present. 
  • Turn on showers and taps for two minutes - preferably at a high temperature, if they have not been used for more than a week, and flush toilets with the lid down.
  • Keep all your showerheads and taps clean and free from a build-up of limescale, mould or algae growth. 
  • Drain any hosepipes after use and keep them out of direct sunlight.
  • Maintain any spas or hot tubs you have. Keep them clean, free from debris and check and clean the filters according to the manufacturer’s instructions. If you haven’t used the spa or hot tub for a while, change the water before using it.

I am an employer, what can I do to prevent Legionnaires’ disease

If you are an employer, or someone in control of premises (e.g. landlord), you have a legal duty to understand and manage legionella risks.

You must understand how to:

For further information visit the Health and Safety Executive Website

What should you do if you think you have Legionnaires'?

In the UK you are advised to phone 111 or go to 111.nhs.uk if you have a bad cough and:

  • It does not go away
  • You cannot breathe properly
  • You have severe chest pain
  • You have a high temperature or feel hot and shivery
  • You feel like you have severe flu

Why is it called Legionnaires' Disease?

In 1976, in Philadelphia there was an outbreak of the disease amongst people attending a convention of the American Legion and 29 people, mostly men, died. When the disease was identified it was named Legionnaires' disease. 

Later, in 1977, the causative agent was identified as a previously unknown strain of bacteria, subsequently named Legionella, and the species that caused the outbreak was named Legionella pneumophila.

Medically, the illness is named Legionellosis, but Legionnaires' disease is the more common name.

Legionella awareness training courses for ACoP L8 compliance

Topics: Legionella Control, Legionella

Alex Winter

Written by Alex Winter

Alex is a Marketing Contributor and has 5+ years in water treatment and ACoP L8 compliance and works across all six linked areas of the business; Water Treatment, Waste Water, Water Hygiene, Air Hygiene, Engineering and Legionella Training.