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Legionnaires' disease

Legionnaires' disease is a lung infection. You can get it by breathing in small water droplets in the air containing the bacteria that causes it. It's rare but can be very serious.

How you get Legionnaires' disease

It's usually caught in places where water has the potential to stagnate, such as hotels, hospitals or offices, and the bacteria has got into the water supply.

Stagnant water is water that is not moving or flowing.

You can catch it from things like:

  • air conditioning systems
  • humidifiers
  • spa pools and hot tubs
  • showers, taps and toilets
  • compost, potting mix and any form of soil or dirt in warmer countries

It's rare to catch it at home.

Check if you have Legionnaires' disease

Legionnaires' disease usually starts with flu-like symptoms.

This includes:

  • fever
  • tiredness
  • headache
  • muscle pains

This is followed by:

  • a cough
  • difficulty breathing
  • chest pain
  • a high temperature

Urgent advice: See your GP urgently 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

You should contact your GP and tell them where you have been in the past 10 days, for example if you stayed in a hotel, spa or hospital.

Emergency action required: Go to your nearest emergency department (ED) if you are:

  • unable to contact a GP
  • very unwell

Treatment for Legionnaires' disease

You may need to go into hospital if you're diagnosed with Legionnaires' disease.

Treatment in hospital may include:

  • antibiotics directly into a vein
  • oxygen through a face mask or tubes in your nose
  • a machine to help you breathe

When you start to get better you might be able to take antibiotic tablets at home for 1 to 3 weeks.

Most people make a full recovery, but it might take a few weeks to feel back to normal.

Preventing Legionnaires' disease

The best way to prevent Legionnaires' disease is by taking proper care of any water supply where the bacteria can grow.

Let water run through shower heads or taps that are not in use once a week for at least 5-10 minutes.

The water that runs through should be a temperature of:

  • 50 degrees Celsius or higher for hot water taps
  • 20 degrees Celsius or lower for cold water taps

This is because the bacteria that causes Legionnaires' disease grows best in water temperatures between 20 and 45 degrees Celsius.


Do not use hot water above 50 degrees Celsius to prevent scalding. Especially children and older people.

Lower the water temperature before using it.

Hot water from taps

Regularly maintain and clean your showers, shower heads and water taps to avoid a build up of dirt.

Page last reviewed: 11 July 2023
Next review due: 11 July 2026

This project has received funding from the Government of Ireland’s Sláintecare Integration Fund 2019 under Grant Agreement Number 123.