What is Legionella?

  • Legionella pneumophila is a rod-shaped bacterium which belongs to the genus Legionella.
  • Around 58 species of Legionella have been identified with L.pneumophila responsible for approx. 90% of cases of disease in humans.
  • Legionella bacteria is naturally occurring and can be found in water courses, soils, composts and other aquatic environments.
  • At low temperatures (under 20ºC) the bacteria can survive but do not multiply as they are rendered dormant. Temperatures of 50ºC + will start to kill legionella bacteria with temperatures of 60ºC+ having over a 90% kill rate.
  • The bacteria multiply rapidly in nutritious environments created by biofilm and sediment.
  • Legionella bacteria can only infect your body through inhalation of contaminated water droplets often referred to as an aerosol.

Legionella bacteria flourish under certain conditions:

  • Temperature between 20-50oC with optimum growth occurring at a temperature of 37oC.
  • Little or no water movement as stagnant water provides an excellent breeding ground for the bacteria.
  • Water systems which enhance the spread of bacteria through producing aerosols/ water vapour which can then be inhaled.

High risk systems which produce water vapour/aerosols include:

  • Showers taps and baths (especially spray taps).
  • Cooling towers.
  • Air conditioning units.
  • Hot tubs/ Jacuzzis.

Origins of Legionnaires' Disease

Infection by Legionella bacteria causes Legionnaires’ Disease which is a potentially fatal form of pneumonia and typically affects men more than women. It is not contagious but it can be fatal. The disease was first identified in 1976 after an outbreak at the convention of the American legion in Philadelphia where over 220 people were infected resulting in 34 deaths.

Since then, numbers of cases have slowly risen with latest figures showing 200-250 reported cases of Legionnaires’ disease each year in the UK.

The risk of contracting the disease from a contaminated water source is minimised by following the Approved Code of Practice by the HSE (ACoP L8).

Who is at risk?

Everyone is susceptible to infection, but there are those who are at higher risk:

  • Those over 45 years of age.
  • Smokers and heavy drinkers.
  • The elderly and infirm.
  • Those suffering from chronic respiratory or kidney disease.
  • Those with impaired immune systems e.g. transplant patients.

Fatality Rate

Infection can be fatal in approximately 20% of reported cases. This rate can be higher in a more susceptible population.

A milder form of the disease known as Pontiac fever or Lochgoilhead fever can be contracted by those who have healthier immune systems. These symptoms are typically flu-like and are usually less severe.

Your Legal Duties

As a person who is responsible for water systems you have certain duties under Health and Safety law. The Health and Safety at Work Act 1974 (HSWA), Control of Substances Hazardous to Health Regulations 2002 (COSHH) and Management of Health and Safety at Work Regulations 1999 (MHSWR) all cite the HSE’s Approved Code of Practice L8 as the recommended guidelines for the management of risk of exposure to Legionella.
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