It is a disease caused by a bacterium called LEGIONELLA PNEUMOPHILA. Infection is caused by breathing in a fine spray of airborne water which carries the bacterium. There is no evidence to show that you can get the disease from someone who has already been infected or from drinking water carrying the bacterium.
Between 100 to 200 cases of Legionnaires' Disease are reported each year in England and Wales. The disease starts with high fever, chills, headache or muscle pain. A dry cough and pneumonia soon develop and although most people recover this can be a serious disease and in some cases is fatal.
Those most at risk include smokers, alcoholics and patients with cancer, diabetes, chronic respiratory or kidney disease. However you could be infected even if you are healthy.
Most cases have been in people aged between 40 and 70 years; men are more likely to be affected than women.
The LEGIONELLA bacterium is found in natural water supplies and in soil. It is also found in many recirculating and hot water systems. Outbreaks have occurred in or near large building complexes such as hotels, hospitals, offices and factories. There is no evidence that water systems in domestic homes present any risk.
If Legionella is so widespread why aren't there more outbreaks?
All infections are caused by people breathing contaminated water sprays from equipment such as air conditioning plant, cooling towers, industrial sprays and showers.
Special conditions are needed in water systems before the bacterium multiplies. These include: -
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the presence of sludge, scale, rust, algae and organic matter;
a water temperature in the range 20C to 45C |
Fortunately the combination of circumstances required to result in an outbreak does not occur very often.
Since the LEGIONELLA bacterium is widespread, you cannot prevent it from entering water systems. However, the risk of an outbreak developing can be reduced by taking the following precautions:-
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Hot and cold water services
tanks and pipe work should be designed so that water is not allowed to stand undisturbed for long periods;
tanks should be well covered to prevent the entry of dirt, debris and vermin, and should be periodically inspected, cleaned and disinfected;
water temperatures between 20 0 C and 45 0 C should be avoided; eg by storing hot water at 60 0 C and circulating it at 50 0 C (beware of scalding);
water system fittings and materials complying with the water authority by-laws should be used (certain materials, eg leather, some rubbers and plastics, support the growth of bacteria and should not be used).
Cooling towers
cooling towers and their associated water systems need to be well designed, maintained and operated; the fitting of drift eliminators which reduce the escape of spray is especially important;
systems should be cleaned and disinfected at least every six months;
water should be treated to prevent corrosion and microbiological growth, including the multiplication of bacteria;
it may sometimes be possible to replace cooling towers with dry cooling systems.
Other water systems
Precautions are necessary wherever water conditions are ideal to support the growth of the bacterium and there is a means of dispersing droplets, eg commercial spa baths and humidifiers |
Hospitals and the Public Health Laboratory Service monitor monitor the incidence of Legionnaires' Disease so that outbreaks can be quickly identified and not confused with isolated cases, many of which result from holidays or visits abroad.
As soon as an outbreak is suspected a team of specialists mount an investigation to:-
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identify the source;
identify the people likely to be affected;
ensure the contaminated water system is treated as quickly as possible. |