Legionnaires' Disease / Legionellosis

Legionnaires’ disease is an uncommon, severe type of pneumonia caused by Legionella bacteria, often requiring intensive care treatment in hospital. Legionellosis can be fatal and death can occur in approximately 10-15% of otherwise healthy people.

A mild form of Legionnaires' disease, known as Pontiac fever, may produce signs and symptoms including a fever, chills, headache and muscle aches. Pontiac fever doesn't infect your lungs, and symptoms usually clear within two to five days.

Legionella bacteria are found in many types of water systems. The bacteria multiply in warm, and stagnant water, such as can be found in air conditioning cooling towers, certain plumbing systems especially showers, spa pools, decorative fountains, sprinklers and nebulisers. The infection is spread through the air from the water source. People become infected when they breathe in aerosols (tiny droplets of water) which have been contaminated with Legionella bacteria. There is no evidence of spread from person-to-person. A type of Legionella bacteria has also been found in potting compost, particularly in warm countries, and gardeners can be infected by breathing in the bacteria through water droplets, dust or from hands contaminated with compost. Legionellosis is very uncommon, with low numbers of infections notified every year in Ireland. Legionellosis is a notifiable disease in Ireland.

Last updated: 21 March 2024

Aug 2024

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Legionnaires' disease outbreak in Italy (Milan area)

• Legionnaires' Disease - Factsheet for the public
• Legionnaires' Disease - Factsheet for GPs

Checklists

Legionnaires' disease - Checklist for gardeners

File Size: (30kb)
Publication Date: 9 July 2018

Legionnaires’ Disease - Checklist for leisure centres

File Size: (702kB)
Publication Date: May 2017

Legionnaires' Disease - Checklist for hotels and other accommodation sites

File Size: (99kB)
Publication Date: 6 July 2016
ECDC - Leaflet for managers of tourist accommodation on how to reduce the risk of Legionnaires' disease

Legionnaires' Disease - Checklist for hostels providing accommodation for people who are homeless

File Size: (84kB)
Publication Date: 17 June 2016