Business & compliance advice

Legionella - The symptoms to look out for

26th February 2018

Treatment of Legionnaires’ disease is by antibiotics, and early recognition and treatment are important for survival. The symptoms vary, depending on whether it is mild or severe.


Mild (sometimes called Pontiac fever) has a 24 to 48-hour incubation period, followed by 2 to 5 days of influenza-like illness. Severe Legionnaires’ disease usually has a 2 to 10-day incubation period, but it can be up to 20 days. It generally involves acute and rapid pneumonia with other symptoms such as:

  • Headache

  • High fever

  • Muscle pains

  • Cough

  • Breathing difficulties

  • Loss of strength

  • Confusion

  • Diarrhoea

Who's at risk?

The risk increases with age, and those with a higher risk include:

  • Over-45s

  • Smokers and heavy drinkers

  • People suffering from chronic respiratory or kidney disease

  • Diabetes, lung and heart disease

  • Anyone with an impaired immune system

Conditions to avoid, because Legionella loves them

People contract Legionnaires' disease by inhaling small droplets of water (aerosols) that contain the bacteria and are suspended in the air they breathe. Certain conditions within man-made water systems can lead to the growth and spread of the bacteria including:

  • Water between 20-45°C, optimum temperatures for Legionella growth

  • The aerosol process, dispersing water into breathable water droplets

  • Stagnation of water due to storage and/or recirculation This encourages the formation of biofilm, a thin layer of microorganism slime that feeds the bacteria

Visit our Legionella Awareness Course page to find out more and book the course.