How Does Legionella Infect People 1991 HSE

Legionnaires' disease is an uncommon form of pneumonia caused by the legionella bacterium. The majority of cases are reported as single (isolated) cases but outbreaks can occur. People become infected when they inhale legionella bacteria which have been released into the air in aerosolised form from a contaminated source. Once in the lungs the bacteria multiply and cause either pneumonia or a less serious flu like illness (Pontiac fever ). The bacteria are widely distributed in the environment. They can live in all types of water including both natural sources such as rivers and streams, and artificial water sources such as water towers associated with cooling systems, hot and cold water systems and spa pools. They only become a risk to health when the temperature allows the legionellae to grow rapidly, such as in building water systems which are not properly designed, installed and/or maintained. Control and prevention of the disease is through treatment of the source of the infection, i.e. by treating the contaminated water systems, and good design and maintenance to prevent growth in the first place. All ages can be affected but the disease mainly affects people over 50 years of age, and generally men more than women. Smokers and the immunocompromised are at a higher risk. The disease was first identified from an outbreak of this disease that occurred in Philadelphia in 1976, among people (Legionnaires) attending a state convention of the American Legion and led to naming the disease after this group. Although the disease was identified in 1976, cases have been confirmed as far back as 1947 and some probably also occurred before then. The early symptoms of Legionnaires' disease include a 'flu-like' illness with muscle aches, tiredness, headaches, dry cough and fever. The incubation period can range from 2 to 19 days with a median of 6 to 7 days after exposure. For more on Legionnaires' disease, go to http://www.hse.gov.uk/legionnaires/whatis.htm . This is clipped from the 1991 film Legionnaires' disease by the UK Health and Safety Executive and available at the Wellcome Library at http://catalogue.wellcome.ac.uk/ .

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