Legionella bacteria are common in natural and artificial water systems and can proliferate in poorly maintained wet cooling systems or hot and cold water systems in a wide variety of places e.g. hospitals, office buildings, industrial premises, showers and even fountains. Organisms thrive between 20 and 45 degrees centigrade. They are killed at higher temperatures and this is the main method used for their control in hot water systems. Legionellosis is the name given to a group of pneumonia-like illnesses caused by legionella. The most serious is Legionnaires' Disease and there have been several large outbreaks involving staff, patients or the general public.
Infection is caused by breathing small droplets of water contaminated by the bacteria.
Anyone can get infected but those most at risk include elderly people, smokers, alcoholics and those suffering from cancer, diabetes, chronic respiratory disease or kidney disease. Control of legionella in evaporative cooling towers and hot and cold water systems is required under the Health and Safety at Work Act 1974. Guidance on legionella was first issued by HSE in 1987. These are all available from HSE Books telephone 01787 881165. This is intended to identify possible sources of infection during investigations of outbreaks of Legionnaires' Disease.