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Lisa Scholl

Lisa Scholl


Legionella symptoms: recognize and treat the disease

Legionella are rod-shaped bacteria that are a component of fresh water worldwide. Especially in the water pipes of buildings the optimal conditions for the growth of environmental germs prevail. Legionella infection can have far-reaching consequences for human health. In this article, you will learn how the pathogens enter the human body, which symptoms can be used to detect legionellosis and which treatment methods are possible.

Legionella are rod-shaped bacteria that are a component of fresh water worldwide. Especially in the water pipes of buildings the optimal conditions for the growth of environmental germs prevail. Legionella infection can have far-reaching consequences for human health.

In this article, you will learn how the pathogens enter the human body, which symptoms can be used to detect legionellosis and which treatment methods are possible.

What are legionella?

Legionella are rod-shaped bacteria that are distributed worldwide in surface water and groundwater or drinking water. The pathogens with the scientific name Legionella pneumophila can cause very different clinical pictures of legionellosis in humans – from mild flu-like symptoms such as fever to severe pneumonia.

The optimal growth conditions for Legionella are in warm water at temperatures between 25 degrees and 50 degrees. On the other hand, as soon as the temperature of the water drops below 20 degrees, Legionella hardly multiply. The pathogens are not killed until the water temperature exceeds 60 degrees.

Legionella can multiply particularly quickly in the water systems and water pipes of buildings due to the ideal temperature. In addition, the deposits in the pipes – also called biofilm – provide the ideal breeding ground for the bacteria.

How can you get infected?

Infection with Legionella usually occurs via water droplets containing the pathogen. They are transmitted by atomized or nebulized water. Especially the water vapor produced in the shower can cause the bacteria to spread in the air and subsequently be inhaled through the lungs.

For example, showers, whirlpools, faucets, air conditioners, and even humidifiers are dangerous sources of infection. However, there are many other sources of infection that may be considered.

Contrary to popular misconception, however, there is no risk of infection when drinking, since in most cases Legionella infection is caused by inhaling the bacteria into the lungs . In addition, human-to-human transmission should also be excluded as far as possible.

Across Germany, approximately 1.7 cases per 100,000 population were reported in 2018. However, the number of unreported cases could be significantly higher, as not all recorded pneumonias were attributed to legionellosis.

These are the symptoms

Legionella infection does not necessarily cause severe symptoms of disease in all cases.

Whether legionellosis causes a mild or severe course of disease depends on a wide variety of factors:

  • Type of recording

  • Number or quantity of ingested legionella bacteria

  • Type of pathogen → Legionella of the genus Legionella pneumophila , for example, is considered particularly problematic for humans.

  • Defense status of the affected person → People with a weakened immune system may suffer a significantly more severe course of disease with more severe symptoms than people with a well-functioning immune system. In addition, pre-existing conditions such as diabetes mellitus or certain medications can affect the functioning of the immune system.

  • Age of the patient → Elderly people and babies and young children usually suffer a more severe course of the disease.

  • Lifestyle → Smokers or people who regularly consume alcohol also have an increased risk of contracting legionellosis.

Probably the best known diseases caused by Legionella include Pontiac fever and Legionnaires’ disease.
  1. Pontiac fever is characterized by a rather mild course . It usually occurs after about one to two days after the pathogens have entered the body. In most cases, patients experience flu-like symptoms such as fever, headache, aching limbs, sore throat, and dizziness.

    However, within a few days the symptoms subside, so that special treatment is not necessary in most cases. Severe courses of the disease are rarely caused by Pontiac fever.

  2. Legionnaires’ disease , on the other hand, is a severe form of pneumonia. The incubation period of the so-called Legionella pneumonia is usually two to ten days. Then the first symptoms already show themselves.

    Often the disease begins very suddenly. It manifests with high fever of up to 40 degrees, chills, general malaise, and headache and muscle pain. In addition, Legionnaires’ disease causes typical symptoms of pneumonia such as severe cough, chest pain and shortness of breath. In this regard, Legionnaires’ disease is often indistinguishable from normal pneumonia.

    Furthermore, Legionella infection of this type can lead to gastrointestinal symptoms such as abdominal pain, diarrhea and vomiting. If the patient’s nervous system is also affected by legionellosis, this can cause a state of confusion.

    Both the symptoms of Legionnaires’ disease and the disease itself require mandatory treatment. Appropriate therapy can bring about a rapid reduction in symptoms. Nevertheless, late effects such as pulmonary fibrosis (scarring of the lungs due to increased connective tissue formation) cannot be ruled out.

This is how it is treated

Pontiac fever caused by Legionella usually heals on its own. Treatment with antibiotics is usually not necessary.

However, in the event of a diagnosis of Legionnaires’ disease, immediate action is required, as the disease can be life-threatening, especially for immunocompromised, chronically ill and elderly people.

Appropriate treatment of Legionnaires’ disease is usually by antibiotics. The administration of the drugs inhibits the growth of the pathogens in the body or, in the best case, kills them completely.

In this case, it is essential to consult a specialist, as not every antibiotic is effective for a Legionella infection. It is not uncommon for Legionella to take refuge in the body’s phagocytes (“scavenger cells”), so that antibiotics from the fluoroquinolone group have to be used. These are supposed to act inside the cells and fight the legionella in the body. Particularly severe cases of Legionnaires’ disease may even require a combination of different antibiotics .

Treatment of Legionnaires’ disease may continue for several weeks until the infection and its symptoms have completely resolved.

Showering with Legionella – Mouth protection necessary?

The most common source of Legionella infection is the shower. If there is a confirmed legionella infestation, a complete shower ban can be imposed, among other things, if the value of 10,000 cfu is reached.

Using a mouthguard while showering, on the other hand, is not an appropriate protective measure to guard against Legionella infection. It is better to switch the water temperature of the central water heater to above 60 degrees, so that the legionella in the water is killed even before an infestation. For this, the hot water should run through the pipes for several minutes. In case of doubt, it is advisable to ask the health department for suitable measures to protect against legionella. Legionella filters protect against possible infection.


The first symptoms of a Legionella infection usually appear between two and ten days after the pathogen has entered the body.

If Legionella is suspected, a specialist should be consulted immediately. The exact diagnosis is usually determined by a chest X-ray and a special urine or saliva test. Proper treatment of Legionella pneumonia requires the use of antibiotics.

Basically, legionellosis causes flu-like symptoms in the body, such as Pontiac fever. In more severe cases, Legionnaires’ disease can also occur, which manifests as a severe form of pneumonia.

On average, the disease lasts for seven days. However, if white blood cells have been severely reduced as a result of Legionella infection, the course may be prolonged.

Yes, a legionella infestation can be checked by yourself with the help of special test kits. All you have to do is send a sample of tap water to a laboratory and you will receive the result.

In principle, experts assume that transmission of legionella through drinking contaminated water can be largely ruled out.


Legionella infection may well have serious consequences for human health. Affected individuals may not only suffer from mild, flu-like symptoms, but may also have to deal with severe complications, such as Legionnaires’ disease.

If the first symptoms appear, it is advisable to consult a specialist immediately in order to start appropriate treatment as soon as possible. However, there is no need to be afraid of legionella in water in Germany. Most buildings have a special legionella circuit that heats the water to 70 degrees once a week to kill any legionella that may be present.


Legionella filter shower – advantages and operation of the filter system.

Drinking water in Germany is subject to strict quality standards and can generally be used without hesitation, both for consumption and for personal hygiene. In some cases, however, hot drinking water from the tap or shower can also be contaminated with harmful bacteria – the so-called legionella.

This article shows why the use of a legionella filter makes sense and which types of filters can be used.

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Finding the right faucet – This is what matters

If the existing faucet needs to be replaced, or in the course of new construction, builders decide to install the faucets themselves, sooner or later the question arises: How to fix a faucet in the kitchen or bathroom?

But do not worry: installing a faucet is anything but laborious or complicated. But how to find the right faucet, why is the planning phase crucial and how to turn on the new faucet? This article provides step-by-step instructions for beginners!

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