The good news comes with autumn: As temperatures fall, the risk of further malaria transmission in Germany also decreases significantly. However, the current cases reported in the vicinity of Frankfurt Airport show that, in very rare cases, malaria can occur in Germany even without previous travel abroad. In such cases, early diagnosis is crucial.
“We are dealing with a very rare event, not a new everyday disease in Germany,” emphasises Prof. Achim Hörauf, Director of the Institute of Medical Microbiology, Immunology and Parasitology (IMMIP) at Bonn University Hospital (UKB). “In cases of high, unexplained fever, it may currently also be important to ask whether the person has previously been at Frankfurt Airport or in the surrounding area – even if they have not travelled abroad.”
An imported mosquito can be enough
Malaria is not transmitted directly from person to person. Infection requires the bite of a female Anopheles mosquito carrying the malaria parasite.
“A mosquito can, for example, become trapped in a suitcase, clothing or other luggage and be transported to Germany in this way,” explains Prof. Hörauf, who is also member of the ImmunoSensation³ Cluster of Excellence. “In heated areas of an airport, it may initially find suitable conditions and survive for some time.” Such infections are therefore also referred to as airport malaria or “baggage malaria”. A single infected mosquito can bite several people during its lifetime and transmit the parasite.
However, several factors must come together for transmission to continue over a longer period. The mosquitoes must survive and remain active for long enough. If a mosquito acquires the parasites through a blood meal shortly before being inadvertently transported to Germany, sufficiently high temperatures are also required for the parasites to continue developing inside the mosquito.
Falling night-time temperatures slow transmission
As autumn sets in, conditions become less favourable for both mosquitoes and parasites. The falling temperatures at night are particularly important. Mosquitoes become less active, their reproduction is reduced and their lifespan decreases. At the same time, development of the malaria parasite inside the mosquito slows down or stops.
Nevertheless, further cases may occur with a delay. With Plasmodium falciparum malaria, the first symptoms usually appear around one to two weeks after the bite of an infected mosquito. Infections acquired during an earlier period of warm weather may therefore only become apparent later.
Why Plasmodium falciparum malaria can become so dangerous
According to current information, the recently reported cases from the Frankfurt area involve Plasmodium falciparum malaria. It is considered the most dangerous form of malaria.
The parasites infect red blood cells and alter their surface. As a result, infected blood cells can adhere to the walls of the smallest blood vessels and impair blood flow to vital organs.
“In simple terms, this can lead to many small blockages in the blood vessels,” explains Prof. Hörauf. “Depending on which organs are affected, this can result in different and potentially severe complications.”
In the lungs, fluid can accumulate and cause severe breathing difficulties. If blood vessels in the brain are affected, so-called cerebral malaria can develop, potentially causing impaired consciousness and neurological damage. Acute kidney failure is also possible. Without rapid treatment, the patient’s condition can deteriorate significantly within a short period of time.
Take high fever seriously, even without travel abroad
Typical symptoms include sudden high fever, chills, headaches and aching muscles and joints. Nausea, vomiting or diarrhoea may also occur. Unlike some other forms of malaria, P. falciparum malaria often does not cause fever at regular intervals.
“The biggest challenge is to think of malaria in the first place,” says Prof. Hörauf. “If the diagnosis is made in time, targeted treatment can be initiated. If the disease is overlooked, however, it can very quickly take a severe course.”
For people returning from tropical regions, the general rule remains: If fever develops after a stay in a malaria-endemic area, malaria must be ruled out. In view of the current cases, the medical history should temporarily include an additional question in patients with high, unexplained fever: Has the person been at Frankfurt Airport or in the immediate surrounding area in the past few days?
Rapid test provides initial indications
If malaria is suspected, a rapid test can provide initial indications. For a definitive diagnosis and identification of the pathogen, parasitological blood tests are required. These include, in particular, the so-called thick blood film and blood smear.
Identifying the specific malaria parasite is important for treatment. Some malaria parasites can form dormant stages in the liver that can become active again months later and cause renewed episodes of illness. These liver stages require additional, targeted treatment. Plasmodium falciparum, which causes P. falciparum malaria, does not form such dormant liver stages.
“Malaria without travel abroad is possible in Germany, but it remains a very rare disease,” concludes Prof. Hörauf. “In cases of high, unexplained fever and a recent stay at Frankfurt Airport or in the surrounding area, malaria should currently be considered as part of the differential diagnosis.”
Scientific contact
Prof. Achim Hörauf
Institute for Medical Microbiology, Immunology, and Parasitology (IMMIP)
ImmunoSensation³ Cluster of Excellence
E-Mail: achim.hoerauf@ukbonn.de
Press contact
Jana Schäfer / Daria Siverina
Deputy Press Officers at Bonn University Hospital (UKB)
Public Relations and Corporate Communications
Phone: (+49) 228 287-19891 / -14416
Email: jana.schaefer2@ukbonn.de / daria.siverina@ukbonn.de
