Legionella

The Legionella bacterium was discovered in the mid-1970s during a congress for American army veterans. The bacterium owes its name not just to the circumstances in which it was discovered ('Legionella' stems from 'legio', the Latin word for a military unit), but also the illness that it can cause: Legionnaire's disease. This illness, officially called 'legionellose', manifests itself in two forms. The most serious form is a potentially fatal pulmonary condition.

Mains water as a source of life
One of the habitats of the Legionella bacterium is mains water. As long as that water is cooler than 25 degrees or warmer than 60 degrees Celsius, there is no problem. In cold water, the bacterium does not multiply and it dies off in water with a temperature higher than 60 degrees. However, if the water temperature is between 25 and 60 degrees, the bacterium multiplies at high speed. It particularly thrives in the slime layers of metal water pipes. Because these slime layers form faster in stagnant water, it is important to make sure that the water in those pipes flows regularly.

Danger from spray
Drinking water that contains the bacterium is not considered to be dangerous. People can be infected, however, by breathing in miniscule drops of water (called aerosols) that contain Legionella bacteria. Systems that spray water, such as showers or fire-fighting systems, therefore require special attention when trying to limit the risk of Legionella.