What is Legionella?

What is Legionella?

  • Legionella pneumophilia is a rod-shaped bacterium which belongs to the genus Legionella
  • Around 50 species of Legionella have been identified with L.pneumophilia responsible for approx 90% of cases
  • It is naturally occurring in soil and water environments
  • At low temperatures (under 20oC) the bacteria survive but do not multiply, over 60oC the bacteria die
  • 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


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.

Do you need a legionella risk assessment?

Legionnaires’ disease is a potentially fatal condition contracted by inhaling small droplets of water containing the legionella bacteria.

Under UK health and safety law, including the Health and Safety at Work etc Act 1974, every business or person in control of premises is required to carry out a regular legionella risk assessment to identify possible sources of legionella in their building, and take action to control the risk if necessary.

Stara Water Hygiene are a Specialist Water Hygiene company with extensive knowledge and expertise, We can provide a wide range of services to help control and minimise the Risk of Legionella exposure.

Choose us for your Legionella/Water Hygiene services and we’ll help you ensure your water supply is clean, safe and you remain Compliant.