Legionella

Legionella is a bacterium that can cause legionellosis, a disease that has over 40 different variants. The most well-known types are legionella pneumonia (also referred to as Legionnaires' disease or legion fever) and legionella influenza (also known as Pontiac fever).

The name "Legionnaires' disease" comes from an outbreak that occurred among veterans in Philadelphia in 1976, which ultimately led to the identification of this illness. Most people exposed to Legionella bacteria do not become ill. However, some may experience mild, flu-like symptoms. In severe cases, the infection can lead to serious pneumonia, known as Legionnaires' disease.

The Legionella bacterium (Legionella pneumophila) is naturally found in water and soil. Infection can occur when the bacteria are inhaled, but drinking contaminated water does not cause a health risk. Legionella is almost never transmitted from person to person. The risk of becoming infected arises when water is aerosolised, allowing tiny droplets to be inhaled. Common sources include spraying water from showers, garden hoses, and hot tubs. Additionally, wet cooling towers, which release mist to cool buildings, can also be a source of infection.

Where does Legionella occur?

Legionella bacteria can be found all over the world. They grow quickly in warm, stagnant water and thrive at temperatures between 25 and 45 degrees Celsius.

What are the symptoms?

Infection with Legionella can make people very ill, often requiring hospitalisation. The symptoms include:

• High fever
• Shortness of breath
• Pain when breathing
• Cold chills
• Headache
• Vomiting
• Diarrhoea

How to prevent Legionella?

There is no vaccine or inoculation available against Legionella bacteria. However, you can take steps at home to reduce the risk. For example, set your boiler to a high temperature (at least 60 degrees Celsius), drain the garden hose after use, and decalcify the shower regularly. Hot tubs or Jacuzzis should also be cleaned frequently. Quitting smoking can help lower the risk of Legionella infection. When travelling, it may be more challenging to take these precautions. However, showers, garden hoses, and Jacuzzis that have not been used for a long time can cause a higher risk. It is recommended to flush pipes and showers with hot water for a few minutes before use, as this can kill the bacteria.

More information

Would you like to know more about Legionella and Legionnaires' disease? Please visit the RIVM information page: Legionella | RIVM.