At a glance
- Incubation period, Legionnaires' disease
- 2 to 10 days (usually 5 to 6)
- Incubation period, Pontiac fever
- 5 to 72 hours (usually 8 to 24)
- Case-fatality rate (RKI)
- community-acquired 5 to 9 %, hospital-acquired around 13 %
- Diagnostic standard
- Legionella urinary antigen test
- Notifiable disease
- § 7 (1) IfSG, by name
Why the illness is often underestimated
The early symptoms of Legionnaires' disease resemble a flu-like infection. That is exactly where the danger lies: what looks like a harmless cold can develop into a life-threatening pneumonia, especially in older, immunosuppressed or chronically ill people.
Symptoms of Legionnaires' disease and Pontiac fever compared
| Legionnaires' disease | Pontiac fever | |
|---|---|---|
| Incubation period | 2 to 10 days (usually 5 to 6) | 5 to 72 hours (usually 8 to 24) |
| Pneumonia | yes | no |
| Leading symptoms | high fever, cough, shortness of breath, headache and aching limbs, sometimes diarrhoea or confusion | flu-like, fever, muscle pain, dry cough |
| Course | severe, hospital treatment often required, case-fatality rate around 5 to 9 % | usually subsides after a few days |
| Treatment | targeted antibiotic therapy | usually symptomatic |
Figures on incubation period, symptoms and case-fatality rate according to Robert Koch Institute, RKI-Ratgeber Legionellose.
Who is particularly at risk?
Not every contact with Legionella leads to illness. Whether an infection develops depends strongly on immune status and pre-existing conditions. The RKI identifies several groups with a markedly increased risk:
- Older people: Around 75 to 80 percent of reported cases are over 50 years of age.
- Men: They fall ill about two to three times as often as women.
- Smokers and people with chronic lung diseases whose airways are already damaged.
- Immunosuppressed people, for example on corticosteroids or other immunosuppressive therapy.
- People with underlying conditions such as diabetes mellitus or chronic heart disease.
In hospitals and care facilities, this exposure reaches the most vulnerable group of all. That is why the operation of the drinking water installation there has to be monitored particularly carefully.
When to see a doctor and how it is treated
The symptoms of Legionnaires' disease cannot be distinguished from ordinary pneumonia. High fever with cough and shortness of breath should be assessed by a doctor, especially if there was possible exposure in the past two weeks, for example through showering in a hotel or a rarely used system. Mentioning such a stay helps with the diagnosis.
The fastest way to detect it is the Legionella urinary antigen test, which is the most common method today, supplemented by testing of respiratory samples. However, the test has to be ordered specifically. If Legionnaires' disease is identified, targeted antibiotic therapy is given. An early start of treatment clearly improves the prognosis. Pontiac fever, by contrast, usually clears up on its own and is treated only symptomatically.
Notifiable disease and what operators must do
Laboratory detection of legionellosis is notifiable under the German Infection Protection Act. The public health authority investigates the possible source of infection and, in doing so, also checks whether the operator of the drinking water installation has met and documented their obligations. For operators, the best protection is therefore prevention: correct temperatures, regular water exchange and complete, continuous documentation.
Testing requirements and intervals