West Nile virus first transmitted in Germany from mosquitoes to humans

In Germany, the first case of West Nile virus has become known, in which a person has become infected by a mosquito bite. As the Robert Koch Institute reported, the 70-year-old man from Saxony had contracted encephalitis and was treated at the St. Georg Hospital in Leipzig. In the meantime the patient had recovered.

West Nile viruses are originally from the African continent. In most cases, certain mosquitoes provide transmission of the pathogen. Birds are the main hosts of the virus. Mosquitoes often become infected when they sting the animals and can then pass on the pathogen to humans. For this reason, many outbreaks occur along typical routes of migratory birds.

Infection is usually mild

The infection runs at about 80 percent without discomfort. About 20 percent show mild illness symptoms such as fever, rash and flu-like symptoms, this is called West Nile fever. Transfers are also possible through blood transfusions.

However, less than one percent of all sufferers - usually older people with pre-existing conditions - experience meningitis (meningitis) or, less commonly, brain inflammation (encephalitis), which can be fatal. In the affected patient, no significant pre-existing conditions were known.

Last year, a veterinarian from Bavaria had already been infected with the West Nile virus during the autopsy of a dying bearded owl. It was the first known transmission of the West Nile virus to humans in Germany. The current case is now the first transmission by a mosquito bite.

Climate change contributes to the spread of the virus north of the Alps

"The risk of further cases is decreasing as the number of mosquitoes declines in the autumn, but in the coming summers we have to expect further West Nile virus infections," says Lothar Wieler, President of the Robert Koch Institute. "Fortunately, most of the cases are mild."

In recent years, there have been recurrent outbreaks in southern and central Europe as well as in the Black Sea states. In 2018 and 2019, scientists from the Friedrich Loeffler Institute and the Bernhard Nocht Institute for Tropical Medicine in Germany detected more than 70 wild and zoo birds that had died of West Nile virus, particularly in eastern Germany.

"Obviously, the unusually warm summer of the past two years caused by climate change has helped to establish the West Nile virus north of the Alps," says Jonas Schmidt-Chanasit, director of viral diagnostics at the Bernhard Nocht Institute. In this country, the virus is transmitted by native mosquitoes of the genus Culex.

Horses are also increasingly affected this year, according to the researchers. Horse owners are therefore advised to have the animals vaccinated. There are no vaccines or specific therapy for humans yet. Infections can only be prevented by mosquito repellent. The detection of the West Nile virus is notifiable.