What is Legionellosis and Legionnaires’ Disease?

Legionnaires’ Disease is a form of pneumonia caused by inhaling tiny water droplets (aerosols) which are contaminated with Legionella bacteria. It is often fatal but is wholly preventable. Legionellosis is the name given to a range of illnesses caused by Legionella bacteria; as well as Legionnaires’ Disease they include Pontiac fever and Lochgoilhead fever which are milder flu-like illnesses.

How do you get Legionella in water systems?

Legionella bacteria are commonly found in natural water systems such as rivers and lakes where their numbers are usually low and they pose little risk. They grow over a temperature range of 20°C to 45°C. Below this temperature, they survive dormant and as the temperature rises above 50°C they are progressively killed off and will not survive long at temperatures above 60°C. Their ideal growth temperature is around human body temperature, 37°C! Whilst Legionella bacteria are widely found in the natural environment the risk comes when they contaminate man-made water systems, entering at low levels in the incoming water supply or in air-borne aerosols. Many man-made water systems not only provide the ideal environment for legionella to multiply but also involve water sprays which can release dangerous aerosols into the atmosphere.

What does legionella need to thrive?

As well as a water temperature of 20°C to 45°C legionella bacteria need a supply of nutrients which are usually provided by other microbes which are commonly found in the water. In particular, there is a strong relationship between biofilms (microbial slimes), amoebae and the growth of Legionella. Biofilms flourish in warm, stagnant water. As a general rule legionella likes dirty systems which are fouled with corrosion products and scale and dislikes clean water systems.

What must I do?

As an employer, or a person in control of the premises, you are responsible for health and safety and need to take the right precautions to reduce the risks of exposure to legionella. You must understand how to:

  • identify and assess sources of risk
  • manage any risks
  • prevent or control any risks
  • keep and maintain the correct records
  • carry out any other duties you may have

How can Aqua Services UK help?

Services offered for the control of legionella include: