Legionnaires’ disease

[ch 7: pages 132-133]

Legionnaires’ disease is an airborne disease caught by inhaling small droplets of contaminated water. It is not contagious and is not known to spread directly from person to person. It cannot be caught by drinking contaminated water.

Legionella bacteria are common in natural water sources such as rivers, lakes and reservoirs, usually in low numbers. The risk of the disease is present when water is stored or recirculated in man-made water systems. Contamination can develop and spread in purpose-built systems like cooling towers, evaporative condensers, hot and cold-water systems and whirlpool spas, humidifiers, air-washers, emergency showers and indoor water fountains. Problems develop when bacteria spread quickly through water-based systems in warm temperatures (between 20 and 45 degrees Celsius).

The HSE publication Legionnaires’ Disease: The control of Legionella bacteria in water systems (L8), along with supporting Technical Guidance, provides practical advice to employers on how to control the risk of legionella bacteria in water systems.

These and other publications related to this topic are available on the Legionnaires’ Disease pages of the HSE website.

The HSE has also issued specific advice regarding the increased risks of Legionnaire’s disease due to the coronavirus outbreak (see page 124 above).