Topic: Legionnaires Disease
Description
Legionnaires disease is a type of pneumonia (lung infection) caused by the legionella bacteria which are common in the environment and can be found in creeks, ponds and soil. There are various types of legionella bacteria, but the main ones that cause disease in people are Legionella pneumophila (often associated with water in cooling towers) and Legionella longbeachae (often associated with soil or potting mix).
Legionnaires disease is rare in people under twenty years of age. It is NOT an important problem for healthy children or young adults. Usually only a small percentage of people exposed to the bacteria develop the infection. People at high risk of serious illness are those over 50 years of age and who smoke cigarettes and people with a weak immune system eg. those with a medical condition such as chronic lung disease, renal disease, diabetes mellitus or cancer.
Symptoms
The first symptoms of legionnaires disease are non-specific flu-like symptoms including fever, headache and muscle aches. There may also be a mild cough with or without phlegm. Some people may develop diarrhoea, vomiting and abdominal pain. Symptoms usually begin five to six days after breathing in the bacteria, but may be slightly longer.
The illness usually progresses rapidly and the chest infection (pneumonia) symptoms become obvious, with high fever, shortness of breath and chest pain being typical symptoms.
The laboratory diagnosis of legionnaires disease is complicated and often delayed. A blood test is usually taken, but a second blood test three to four weeks later may be needed to confirm the diagnosis. Sometimes tests using phlegm or lung fluid can be used to give a diagnosis. A urinary test is useful in some circumstances.
People who receive early effective treatment usually begin to improve within three to five days.
Transmission
Legionnaires disease is not spread from person to person. The disease is spread by breathing in tiny droplets of moisture that contain the bacteria. Legionella bacteria are common in the environment. They can be found in air-conditioning cooling towers, hot or warm water systems, showerheads, spa baths and even soil and potting mix.
Treatment
A person with legionnaires disease usually needs to be admitted to hospital for appropriate antibiotic treatment and care. Because the progress of the infection can be rapid, it is important that antibiotics be given promptly once the diagnosis is suspected. Without early treatment, the illness can progress to severe illness, kidney failure and death.
Prevention
Prevention of the disease requires control of the bacteria, and is based on the suitable maintenance of equipment that can create aerosols. Keeping a domestic hot water system at a temperature of at least 50C may also reduce the risk of disease transmission.
Hands should be washed thoroughly after working with potting mix and inhaling dust from potting mix should be avoided.
Control
Legionella bacteria are commonly found in the environment and are particularly associated with water. It is therefore important to ensure the regular cleaning/disinfecting of cooling towers, water in spas, decorative fountains and ponds etc.
Help and Assistance
For further information, please contact your local doctor, community health centre or nearest Population Health Branch.
References
Heymann, D., ed. 2004. Control of Communicable Diseases Manual, 18th edition. Washington, DC: American Public Health Association.
Last Updated: 12th October, 2009
Date Valid to: 30th June, 2010
