Watermark Compliance Ltd
Legionnaires' Disease
Legionnaires’ disease was first identified following an outbreak at the Bellevue-Stratford Hotel in Philadelphia in July 1976, where a convention was hosted by the American Legion. Many of the hotel residents experienced illness and 34 out of the 221 affected people died. The investigation following the outbreak determined the cause to be a bacterium called “Legionella pneumophilla” and the infection was given the name “Legionnaires’ disease”.
Legionellosis is a collective term for diseases caused by legionella bacteria including the most serious Legionnaires ’ disease, as well as the similar but less serious conditions of Pontiac fever and Lochgoilhead fever. Legionnaires’ disease is a potentially fatal form of pneumonia and everyone is susceptible to infection. The risk increases with age, but some people are at higher risk, e.g. people over 45, smokers and heavy drinkers, people suffering from chronic respiratory or kidney disease diabetes, lung and heart disease or anyone with an impaired immune system.
Legionnaire’s disease is most commonly associated with the bacterium Legionella pneumophilla sero group 1. It has an incubation period of 5 to 10 days, followed by serious pneumonia symptoms including fever, headache, cough and muscular aches. Other common symptoms include delirium, diarrhoea and vomiting. The infection can be treated with antibiotics; however this is a slow recovery which typically leaves residual lung damage. In approximately 12% of cases it is fatal!
The bacterium Legionella pneumophilla and related bacteria are found in natural water systems such as rivers and lakes, but usually in low numbers. They can enter the mains drinking water supply in low numbers, therefore, can be found in purpose built water systems such as cooling towers, evaporative condensers, hot and cold water systems and spa pools. If conditions are favourable the bacteria can multiply which increases the risk of Legionnaire’s disease.
Although legionella bacteria are widespread in natural water systems the conditions are rarely conducive for people to catch the disease. Outbreaks and infections occur from exposure to legionella growing in purpose built systems where water is maintained at a temperature favourable to encourage growth, i.e. between 20 to 45°C.
Legionnaire’s disease is normally contracted by inhaling small droplets of water (aerosols) containing the bacteria. Certain conditions increase the risk from legionella if:
• the water temperature is between 20 to 45°C in some or all parts of the system;
• water droplets (aerosol) can be produced and dispersed;
• water is stored and/or re-circulated;
• there are deposits that can support bacteria growth, such as rust, sludge, scale, organic matter and biofilms.
Legionnaire’s disease is very serious and potentially fatal for those unlucky enough to contract the infection; however it is a mostly avoidable disease! The legionella risk can be managed by implementing control measures which should form part of your legionella risk assessment.
