Legionnaires’ disease infects the lungs and causes potentially fatal pneumonia. It is the most well-known and serious form of a group of diseases known as legionellosis. Other similar (but less serious) conditions include Pontiac Fever and Lockgoilhead fever.
Infection is caused by breathing in small droplets of water contaminated by the bacteria. The disease cannot be passed from one person to another.
Legionella bacteria are common in natural water courses such as rivers and ponds. Since Legionella are widespread in the environment, they may contaminate and grow in other water systems such as cooling towers and hot and cold water services.
They survive low temperatures and thrive at temperatures between 20 – 45°C if the conditions are right, eg if a supply of nutrients is present such as rust, sludge, scale, algae and other bacteria. They are killed by high temperatures.
Employers who manage premises with hot / cold water services and / or wet cooling systems (eg cooling towers and evaporative condensers need to assess and control risks.
Legionella grows well in warm, motionless water and is also found in humidifiers, showers, air washers, mist machines, hot water heaters, whirlpool spas, fountains, hot springs, plumbing fixtures and dentistry tools. Major sources of Legionella include water distribution systems of large buildings including hotels, hospitals and cooling towers.
Prevention of Legionnaires’ disease depends on good maintenance of possible sources, including regular monitoring of water quality, cleaning and disinfection. Ozone has been successfully used in the USA. If possible, keep hot water at above 60°C and cold water below 20°C.
Unfortunately, many cases in South Africa are misdiagnosed as the symptoms are common to other respiratory illnesses, so the scale of the problem is unknown. A few cases have been reported.
Legionella currently falls under the Occupational Health & Safety Act (OHS). Risk assessments need to be performed in line with this regulation.
Due to the larger scale of the problem world-wide, pressure has mounted and a South African Standard is in the process of being developed and is expected to be released some time this year. The reference for the document is SANS 893 (parts 1 – 2).
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