You are here:  Water Pleasure  »  Technology  »  Drinking Water Ordinance  »  What are legionella?

Legionella – Danger from the air

Why are legionella dangerous?

What are legionella?

Legionella are bacteria that live in water. In particular, the legionella type pneumophila can trigger the infamous legionellosis, colloquially known as legionnaires' disease. Legionella find ideal living conditions above all in hot water treatment plants, cold water pipes that are exposed to heat or stagnant pipes (closed pipes which, despite being closed, are still connected to the drinking water system): They prefer places with a temperature between 25 °C and 50 °C, fresh water feeding and prolonged periods of inactivity.

How are legionella transmitted to humans?

Legionella are normally only hazardous to humans when they are inhaled through steam. A healthy person can theoretically drink water infested with legionella without getting sick, but whereby there is also the risk of infested water entering the air passages due to a reduced swallowing reflex, for example. But a fine spray mist, which can be inhaled, is generated through showers, whirlpools, saunas or lawn sprinklers. If the water is infested with legionella, this can lead to infection.

How does legionellosis manifest itself?

The mild form of this disease is called Pontiac fever. It manifests itself after two to a maximum of five days of incubation through flu-like symptoms such as sore throat, fever, headaches and joint pains. Pontiac fever usually passes off without treatment after a few days; isolated cases are not notifiable in accordance with the Infection Protection Act.

In more serious cases of legionnaires' disease, sudden symptoms usually occur after approximately 10 days of incubation, such as high fever, shivering, dry cough, chest pains and breathlessness. Legionnaires' disease can result in pneumonia, which can be serious and even life-threatening. If the nervous system is also attacked, the patient can become dizzy or even confused.

An initial diagnosis can be made by a urine sample, whereby only some types of legionella can be verified. A sure way would be to take a sample from the lung. Legionnaires' disease is notifiable in accordance with the Infection Protection Act.

How often does an infection from legionella occur?

690 cases of legionellosis were recorded by the Robert-Koch-Institut in 2010, as shown by the 2009/2010 annual statistics of notifiable diseases according to federal state. However, it is assumed from these figures that several cases were unreported and that approx. 4% of all cases of pneumonia were triggered by legionella. This is why, with around 500,000 cases of pneumonia recorded per year in Germany, very different figures present themselves according to a Statement of the German Federal Environment Agency :

"Every year, at least 20,000-32,000 people in Germany come down with community-acquired
pneumonia caused by legionella; up to 15 % of cases
even result in death [1, 2]. In addition to this is the even higher number (10-100 times higher) of incidences of Pontiac fever, which is milder and also caused by legionella."

It is difficult to obtain very reliable figures on Pontiac fever, since the illness progresses in a similar way to the common cold and subsides after a few days even without medication. The cause of the symptoms in these cases is usually not investigated at all.