Legionnaires' Disease – The Facts
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Legionnaires' disease was first discovered in July 1976 during an outbreak of severe pneumonia affecting American Legionnaires that had gathered for a convention at the Bellvue Hotel in Philadelphia. The cause was a bacterium that had contaminated a cooling tower on the roof of the hotel – later named legionella pneumophila. Water vapour containing the bacteria had drifted through the ventilation systems and infected the convention delegates.
Legionnaires’ disease is contracted by inhaling small droplets of water suspended in an aerosol or fine mist that contains legionella bacteria. Once in the lungs, the bacteria replicate and produce toxic waste products that cause severe flu like symptoms including:
Fever
Head and muscle ache
Tight chest
Dry cough
Sickness and diarrhoea
Confusion / delirium
There is a 12% – 15% chance of dying from Legionnaires’ disease and those that do survive are often left with permanent disabilities.
Currently about 500 cases are reported each year in the UK and approximately half of these are associated with travel abroad. Men are approximately three times more likely to contract Legionnaires’ disease and the elderly are most susceptible. Risk increases further with heavy smoking, asthma or in hospital patients who may have a weakened immune response.
Legionella bacteria are widespread in low numbers within the natural aquatic environment, however once water is taken into man-made plant and buildings numbers can increase to harmful levels as the conditions suitable for proliferation are more likely.
Outbreaks of Legionnaires’ disease are commonly associated with cooling towers, evaporative condensers, humidifiers, spa pools, and hot water systems as they operate in ideal conditions for legionella growth. Such conditions include:
o Water temperature in the range 20oC to 45oC
o The presence of nutrients such as sludge, scale and rust
o Water stagnation
The presence of a water spray or aerosol provides the means of transmitting the bacteria into the human body.
In order to reduce the risks associated with Legionnaires’ disease, the Health and Safety Executive has produced guidance for property owners and managers. Employers have a duty under the Health and Safety at Work Act to manage the water system in the workplace so that the conditions that encourage legionella growth may be avoided.
For more information about Legionnaires’ disease or managing the risks, please contact Nemco Utilities at www.nemco-utilities.co.uk
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