A seven-year-old boy from Maitenbach, in the Mühldorf am Inn district of Bavaria, recently died of the rare Borna virus. According to media reports, a child from the same place died of the virus in 2019. In mid-August, the neighboring district of Rotall-Inn also reported an infection with the Borna virus. The sick person is currently being treated in hospital, the statement said. The so-called Borna'sche disease is extremely rare. Around 40 cases of the disease have been detected nationwide. According to the Bavarian State Office for Health and Food Safety (LGL), seven people in Germany fell ill with Borna's disease in 2021, five of them in Bavaria. What we know so far about the disease, how it is transmitted and where the virus is found: an overview of the most important questions and answers.
According to the Robert Koch Institute, the "Borna Disease Virus 1" (BoDV-1) has long been known to cause Borna's disease in horses, sheep and other mammals in Central Europe. However, it has only been known for a few years that people can also become infected with the virus and become ill. The virus was first identified in 2018 as the cause of severe meningitis in humans.
In a study published in 2020 in the journal The Lancet Infectious Diseases, researchers examined brain samples from 56 patients. Between 1995 and 2019, they suffered from encephalitis. They were able to detect BoDV-1 in seven cases.
The pathogen must be differentiated from the so-called Variegated squirrel bornavirus, the LGL reports. This can also be transmitted to humans and can cause severe meningitis.
Most of the previous patients had fever, headaches and felt generally ill at the beginning of the infection. According to the RKI, all cases of the disease developed neurological symptoms as the disease progressed, including behavioral problems and speech and gait disorders. Within a few days to weeks, those infected can fall into a coma due to severe meningitis. "The few known cases of illness were fatal with only one exception," says the RKI.
The field shrew is currently the only known natural reservoir. The viruses are probably excreted in the saliva, urine and faeces of the shrew. The route of transmission from shrews to humans has not yet been fully elucidated. However, different transmission paths are conceivable. According to the RKI, it is most likely that people will become infected through the excrements of shrews. The LGL points out that infection is possible through contaminated food or water, or through inhalation of dust contaminated with the virus. Transmission is also conceivable through the bite of a field shrew.
It may also be possible that the virus is transmitted via a so-called intermediate host. This can be, for example, house cats that hunt shrews. Transmission from person to person (outside the medical context, e.g. in transplantations) is extremely unlikely and not known to date. Infected animals other than the shrew - for example horses and sheep are not considered to be infectious to other animals and humans.
According to the Friedrich Loeffler Institute, the virus is largely limited to areas in eastern and southern Germany, as well as Austria, Liechtenstein and Switzerland. The risk areas are marked on a map. Because three cases of the Borna virus have occurred in humans in the western part of the Mühldorf am Inn district, several studies in the district should bring new insights into the infection and possible routes of infection.
The risk of infection can only be reduced by avoiding contact with shrews and their droppings and urine. The LGL advises that if you have a shrew in your home or yard, first identify and remove the food source. This can, for example, be dog or cat food placed outside. If you have to dispose of a dead shrew that the cat has brought with you, for example, you should never do this with your bare hands. Rubber gloves should be worn, and if dust develops, an FFP-2 mask should be worn if possible, informs the LGL. Important: Before the dead mouse and its excreta are removed, it should first be sprayed with cleaning agent - this prevents dust containing the virus from being stirred up. The dead mouse should be disposed of in a well-sealed plastic bag with household waste. Afterwards you should take a shower and wash the clothes you have worn as a precaution.
Shrews are insectivores, not rodents. In contrast to the gray house mouse, its nose is much more pointed. They have small ears and eyes. According to the RKI, the shrews emit a pungent odor. On the belly, the shrew has white fur, while they are brown and gray on top. Encounters between tree shrews and humans are rare. They live in wasteland.
Sources: LGL, leaflet RKI, BMBF, study, communication district Rottal Inn, Friedrich-Loeffler-Institut