Legionella: symptoms and treatment of Legionnaires’ disease
Legionella infections have been known since the 1970s. The bacteria are also found in drinking water and, if ingested by humans in high concentrations, can trigger the dangerous Legionnaires’ disease. In addition, the so-called Pontiac fever is a possible consequence. What are the symptoms associated with these diseases, how do you get infected with the bacterium, and how can you kill Legionella in water and prevent it from multiplying?
What are legionella?
Legionella are rod-shaped bacteria that occur in low concentrations in drinking water. In small amounts, they do not pose a risk to humans – however, if their concentration rises sharply, Legionella can cause the dangerous Legionnaires’ disease.
Legionella occurs naturally in soil and surface water. The bacteria are also contained in the groundwater in small numbers.
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Legionella in drinking water
Due to their occurrence in groundwater, small amounts of Legionella can also be found in our drinking water. In cold drinking water, the concentration is usually deficient because the bacteria only multiply very slowly at temperatures below 20 degrees. At a temperature between 25 and 45 degrees, the multiplication of Legionella runs optimally. If you heat the water above 60 degrees, you can kill Legionella.
Legionella usually multiplies in drinking water when water systems are operated incorrectly or the water is not heated sufficiently. Legionella can also multiply if deposits form in pipes and lines or if water stands still for a long time. This happens mainly when lines are used sparingly. The temperature in the central hot water tank should, therefore, be at least 60 degrees. This reduces the risk of Legionella surviving and multiplying.
How do you get infected with Legionella?
Legionella in drinking water does not pose a problem when drinking, cooking or washing; there is usually no risk of infection here. Infection can only occur by inhaling tiny water droplets – so-called aerosols. This can happen, for example, when showering over the steam. In addition, infection can also occur in swimming pools – for example, by bathing in whirlpools, waterfalls or through contact with other water sprays – and via air conditioning systems.
If you choke on water contaminated with Legionella and this enters the trachea, an infection cannot be ruled out. Infection from person to person is not possible.
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Legionella infection: symptoms and forms of the disease
There are two forms of infection with Legionella – Legionnaires’ disease and Pontiac fever. Both forms cause slightly different symptoms.
Legionnaires disease
Legionnaires’ disease is a severe form of pneumonia. The disease first became known in 1976 after it appeared in some participants at a meeting of US war veterans. These veterans belonged to the American Legion, which gave the disease its name.
The incubation period for Legionnaires’ disease is usually between two and ten days; in extreme cases, it can be up to two weeks.
The following symptoms are typical of Legionnaires’ disease:
Older adults, people with a weakened immune system (e.g. due to chronic diseases or taking certain medications) and smokers have an exceptionally high risk of developing Legionnaires’ disease. Men are also two to three times more likely to be affected by Legionella infections than women.
Pontiac fever
Pontiac fever occurs much more frequently than Legionnaires’ disease. In contrast to Legionnaires’ disease, the incubation period is much shorter, usually just a few hours to three days. Pontiac fever is a flu-like illness that occurs with fever but usually without the involvement of the lungs. The infection usually clears up on its own after a few days.
Symptoms of Pontiac fever are:
- headache
- body aches
- Dry cough
- chest pain
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diagnosis and treatment
Legionnaires’ disease and Pontiac fever symptoms are similar to those of other diseases, so a diagnosis based on symptoms alone is often not possible. Therefore, a urine antigen test (UAT)  can be carried out to identify Legionella as the cause of the symptoms. The urine is examined for Legionella antibodies.
Another way to diagnose is to detect legionella DNA using a PCR test. For example, secretions from the bronchi can be used for the legionella test.
The detection of Legionella is exceptionally reliable by creating a bacterial culture, for example, based on the sputum or bronchial secretions of the person concerned. The disadvantage of this method is that a result is only available after a few days.
In the case of Pontiac fever, the symptoms are treated with appropriate medication. Antibiotics are used to treat Legionnaires’ disease. If the disease progresses severely, hospital treatment may be necessary.
If a legionella infection has been detected, this must be reported to the health department.
Eliminate Legionella in the water.
Finding and eliminating the stove is essential if there is an infestation with Legionella. In addition, it is also important to determine the cause of the infestation – such as a dead water pipe in which the water has been standing for a long time. To remedy the infestation, among other things, heating all the water to over 60 degrees and chemical disinfection with chlorine are possible.
Legionella: testing and limit values
The new regulation of the Drinking Water Ordinance of November 1, 2011, obliges owners of drinking water installations to have their drinking water checked for Legionella at regular intervals. One- and two-family houses are exempt from the inspection requirement.
Specific limit values ​​must be observed when testing drinking water for Legionella. A value of less than 100 CFU/100 millilitres (CFU = colony-forming unit) is acceptable. If the values ​​are between 100 and 1,000 CFU, sanitation must occur within one year. If values ​​above 1,000 CFU are measured, remedial measures must be initiated at short notice. From 10,000 KBE, a danger value is reached, which entails immediate measures such as a ban on showering.
In high-risk areas, the legionella level must be 0 CFU. Examples of high-risk areas include intensive care units, neonatal intensive care units and transplant units. Even on wards where patients with a damaged immune system are treated, such as in oncology, the drinking water must be legionella-free. Special filters achieve this.
