Some Facts About Legionnaires
Disease:
· Caused by the bacterium, Legionella
pneumophila
· First identified after an outbreak of
Legionnaires Disease at the American
Legion convention in Philadelphia,
1976
· Normally contracted by inhaling water
vapour or droplets contaminated with
the bacteria
· Legionnaires Disease is a severe form
of pneumonia, and causes major lung
damage
· Everyone is susceptible, but smokers,
hospital patients, elderly and the very
young are most at risk
· Around 200 cases of Legionnaires
Disease are reported in the UK each
year
· 12% of these cases are fatal
· The true number of cases each year
(unreported), are estimated by clinical
studies to be at 3000-6000 per year
· Legionella pneumophila thrives at
temperatures of 20-50 C. Cooling
Towers and Domestic Hot Water
services are recognised as presenting
the greatest risk
· Growth of Legionalla is greatly assisted
by presence of Biofilm, Scale and
Amoeba
· In the UK, the HSE outlines certain
basic steps that ALL business owners
must take to assess the risk of
Legionnaires Disease, and implement
monitoring and control measures
where appropriate. These regulations
are known simply as “ L8 “ |
Legionella bacteria are present in both natural and manmade water systems, and begin to grow when given the correct conditions of temperature and nutrients.
Conditions within water systems that allow the proliferation of Legionella include stagnation within tanks and pipes, temperatures between 20 and 45oC, accumulations of biofouling within pipes, tanks, and calorifiers, and insufficient disinfection techniques. To reduce the risk of legionellosis, steps must be taken to avoid these conditions.
Unfortunately, many common industrial and commercial water services provide the exact conditions that the bacteria require for growth. When Legionella bacteria are present in high numbers in water sprays or droplets, these can be inhaled into the lungs where they cause Legionnaires Disease.
Legionella is transmitted exclusively by inhalation of contaminated water droplets. LP sero-groups one and six are associated with illness in man. The organisms must be present in sufficiently high concentration and must be suspended in aerosol between 3 and 5 microns in diameter. There is no evidence of disease from ingestion of contaminated water or absorption through the skin. High risk areas are therefore associated with showers, sprays, spray taps, taps with high water pressure, and refrigeration and air-conditioning cooling towers.
Legionnaires Disease is similar to a severe form of pneumonia, the symptoms may include breathlessness, coughing, chest aches, headaches and feeling generally unwell. Legionnaires disease has a low attack rate but with a high mortality rate of around 15%.