Legionella infection (legionellosis) – causes, complaints & therapy

Legionella infection or legionellosis is a bacterial and notifiable disease of the lungs.

Depending on the severity of the disease, two forms are distinguished – the less dangerous variant without pneumonia (Pontiac fever) or classic legionellosis, which can also be fatal due to sometimes severe pneumonia, especially in elderly, chronically ill or immunocompromised patients.

In order to avoid complications, the disease of Legionella infection, which occurs predominantly in the summer and autumn months, must be diagnosed at an early stage and treated with antibiotics.

Causes

Legionellosis is caused by infection with bacterial pathogens (Legionella pneumophila). The Legionella live in fresh water at a temperature of between 20 and 55 degrees Celsius, whereby they can multiply best under conditions between 25 and 45 degrees.While the pathogen in the water usually cannot be dangerous to humans, its inhalation – when water is atomized and bound in the form of aerosol – leads to the infectious lung disease of legionellosis.

Typical sources of infection are, for example, showers in hotels or swimming pools, but also whirlpools, air conditioning systems, drinking water treatment systems, humidifiers and inhalers.

Human-to-human infection is unlikely and has not yet been reported. Elderly and immunocompromised people, patients with severe underlying diseases of the heart and lungs as well as smokers have an increased risk – both in terms of the probability of disease and with regard to a more severe course of Legionella infection.

Symptoms and course

Typical symptoms of Legionella infection:

• Fever

• Ague

• Cough

• Headache

• Body aches

• Nausea

• Stomach ache

Legionellosis manifests itself after an incubation period of two to ten days (in Pontiac fever already after one to three days) by the classic symptom complex of a flu with fever and chills, cough, headache and body aches, occasionally also with nausea and abdominal pain. While the mild variant of Pontiac fever remains with these symptoms, pneumonia (pneumonia) develops in legionellosis due to the multiplication of pathogens in the lungs, which is accompanied by high fever and cough with sputum and carries the risk of spreading the infection to the brain. In about eight percent of all cases – mostly in the classic risk groups or when diagnosed too late – the Legionella infection is fatal.

Diagnosis

The suspicion of a Legionella infection arises from the classic symptoms in connection with informing the patient about recent hotel stays or swimming pool visits. The final diagnosis – especially in contrast to influenza – can only be confirmed by detecting the pathogen in the laboratory. Legionella can be detected by a tissue sample of the lungs, a throat swab, as well as in blood or urine. Since the determination of antibodies in the blood and the cultivation of a bacterial culture in the laboratory are not suitable for rapid diagnosis, a urine sample is used in most cases to secure legionellosis. Because the pathogen can be detected in the urine after only 24 hours, a rapid initiation of therapy against the Legionella infection is possible.

Complications

If the course is severe, the symptoms of a Legionella infection can lead to serious complications. With a fever, there is a risk that the body temperature will rise to over 40 degrees Celsius and cause a circulatory collapse. Due to the gastrointestinal complaints, there can be a severe loss of fluids and, as a result, dehydration and deficiency symptoms. The headaches and body aches that typically occur are primarily a psychological burden, as they usually last for several days. The mild version of Pontiac fever usually causes no further symptoms.

Legionellosis, on the other hand, can cause pneumonia due to the multiplication of the pathogen in the organ. This is accompanied by a high fever with coughing and sputum production. Sometimes the infection spreads to the brain, causing life-threatening encephalitis.

Treatment with antibiotics carries the risk of allergic reactions and side effects or interactions. Classic flu medication can also cause adverse events and lead to serious complications, especially in physically very weak people.

treatment and therapy

Legionellosis must be diagnosed and treated early in order to avoid possible late complications – in the worst case a fatal outcome. For this reason, in many cases treating physicians decide to start treatment as a precautionary measure even if they suspect a legionella infection.

The adequate therapy for legionellosis is to combat the pathogen infestation with antibiotics. Antibiotics should be administered over a period of five to ten days, or for up to three weeks in patients with additional risk factors such as a weakened immune system or other chronic diseases.The antibiosis is supported by the administration of medication, which – as with a cold or flu – is given to alleviate the symptoms. These can be fever reducers, active ingredients against coughs prescribed by the doctor and means to generally strengthen the immune system .

These supportive preparations to alleviate the various symptoms can also be taken in the milder variant of Legionella infection, Pontiac fever. However, antibiotics can usually be dispensed with in this variant, as this form of the disease, in contrast to classic legionellosis, usually heals on its own in a manageable period of time.

Prevention

There is no vaccine to prevent Legionella infection. However, by conscientiously adhering to precautionary measures, a risk of illness can be avoided. You should avoid inhaling the first spray mist from hotel showers, replace shower heads that tend to form aerosols and clean air conditioning, room humidifiers and inhalers regularly to avoid the risk of contamination with the pathogen and possible legionellosis.