08 Gezondheids- en werkplekaspecten
 >  Legionella
Discussion > Discuss this with your colleagues!
  • Sometimes, when I am very thirsty, I will drink from a water hose at the construction site; this is perfectly OK.
  • I never completely flush the water hose during warm weather, because that’s not necessary!

In this toolbox we devote attention to legionalla, a bacterium.

Legionella is a collective name for several groups of bacteria. This bacterium naturally occurs in soil and water. The legionella bacterium grows in water at a temperature of between 20 and 50°C. Above 50°C, the bacterium dies off. You can be infected by a legionella bacterium. In this toolbox we will see how and when legionella can lead to an infection and also how you can avoid this. The bacterium is found in:

  • Rivers and lakes;
  • Warm, slowly flowing or stagnant water; and
  • Humid soil.

The legionella bacterium only grows under favourable conditions, such as:

  • A beneficial water temperature (20-50°C), optimal 37°C;
  • A fertile breeding ground (for example in the sediment of a boiler or in a toilet tank; and
  • Stagnant water.
Risks > What can happen?

Infection takes place through the lungs. The assumption is that the infection is transferred by inhaling the bacterium in very small droplets of water spread through the air. This illness cannot be transferred from one person to another and therefore is not infectious. Drinking the water is not risky.

The infected mist can penetrate to deep into the lungs, where it can cause a lung infection.

Below are a number of situations in which you could become infected:

  • Spraying water, such as taking a shower, fountains or high-pressure sprayers
  • Putting air bubbles into water, such as in bubble baths
  • Certain type of wastewater treatment plants, where air is added to the water
  • Humidification using misting equipment, such as air coolers
  • Wet cooling (water) towers and water installations that cool buildings or industrial processes by atomising water
  • Activities involving ground/soil
  • Splashing rainwater presumably as well

The incubation period, the time between infection and the appearance of the initial symptoms of illness is between 2 to 20 days, with an average of 5 to 6 days.


  • The illness starts with the rapid onset of headache, sore muscles, lack of appetite and a sick feeling. This is followed by a lung infection with fever in excess of 39°C. Other symptoms include coughing, shortness of breath, and vomiting and diarrhoea.
  • The illness can have very serious consequences (fatal), but can be effectively treated with the use of antibiotics.
  • There is no vaccine against this bacterium.

Some people get mild, flu-like symptoms known as the Legionella Flu.

  • These symptoms simply disappear by themselves after a few days.

Risk groups

No risk groups have been established. Most people do not get sick when they inhale the legionella bacteria. Heavy smokers, the elderly and people who consume medications that disrupt their immune system (for example people who have undergone a transplant) are at a higher risk.

Environmental factors

Working in the proximity of aerosol producing systems.

Legionnaires’ disease

Legionnaires’ disease is a serious lung infection caused by the legionella bacterium. This bacterium was discovered in 1976 when an epidemic of lung infections broke out among veterans of the American legion in Philadelphia (USA). It is estimated that each year hundreds, and possibly thousands, of people are infected with the legionella bacterium. Most people do not get sick after exposure. The serious Legionnaires’ disease develops among only a small portion of the people infected with this bacterium.

Measures > What you must do

Preventive measures

  • Inquire about risk identification and evaluation (RI&E) plans and legionella management plans on the basis of the BRL-6010, the Dutch quality standard related to Legionella prevention and control in water systems.
  • Be familiar with the management plan and the measures to be implemented.

Standard measures:

  • Flush pipe lines (every two weeks), for example water hoses/fire hose reels at the construction site.
  • Check the temperature of tap water in hot water lines. This must be above 50°C.
  • Check the temperature of tap water in cold water lines. This must be below 20°C.
  • Ensure there is proper circulation within the system.
  • Clean storage tanks, boilers.
  • Have a water sample taken.

Legionella has been detected, now what?

  • Avoid being infected, in other words ensure you do NOT breathe in any mist!
  • Wear respiratory protection with a P3 filter.
Tips > For more information

Here is some additional information:

Legionella | Netherlands National Institute of Public Health and Environmental Protection (RIVM)

Legionella – InfoMil Knowledge Centre

Scan de volgende code met de app om deze toolbox te bekijken.