Maybe the virus never left the Rottal-Inn district, it’s difficult to say that precisely with this rare and mysterious pathogen. One thing is certain: the Borna virus is here. In the western part of the district, an infection with the life-threatening Borna Disease Virus 1 – BoDV-1 for short – was detected these days. The sick woman is currently being treated in a hospital outside of the district, said a spokesman for the SZ district office. No further information can be given at the moment, one is in contact with the responsible authorities.
The youngest Borna virus case is the third known this year in Bavaria. That sounds like little, is little and is nevertheless striking: Of the approximately 40 BoDV-1 infections that have been detected in humans nationwide in recent years, more than 90 percent can be located in the Free State. The district of Mühldorf is also considered a risk area. At the beginning of August, a child died of an infection in Maitenbeth, it was the second death in the small town since 2019. The virus causes encephalitis in humans, a severe brain inflammation that often ends fatally.
The State Office for Health and Food Safety (LGL) assesses the risk of infection as low: according to the current state of knowledge, transmission of BoDV-1 to humans is very rare. In 2021, a total of seven people in Germany were infected with the Borna virus, five of them came from Bavaria. Nonetheless, experts on the pathogens causing Borna’s disease still cause headaches. It actually triggers animal diseases, in the 19th century it killed numerous cavalry horses in Borna, Saxony. However, the first BoDV-1 infection in humans was not detected until 2018. Accordingly, research into this zoonosis is still in its infancy, and according to the LGL, a trend in the number of infections cannot be read “due to the short observation period”. Outside of Germany, there are other, smaller endemic areas only in Austria, Switzerland and Liechtenstein.
Diagnosing the disease is difficult
The field shrew, which inhabits fallow land, gardens and fields, is considered to be the carrier. As a so-called reservoir host, she probably does not contract the virus herself, but excretes it through saliva, urine and faeces. How exactly it passes from animals to humans is not yet known. It is at least conceivable to become infected through direct contact with the shrew or its legacies, writes the Rottal-Inn district office in a message. “Furthermore, transmission could also occur via contaminated food, water or inhalation of contaminated dust.” Dead shrews should therefore only be removed with rubber gloves and an FFP2 mask, and contaminated surfaces should be cleaned with household cleaners.
Not only does the rarity of the virus make it difficult to diagnose, the symptoms are also rather unspecific at the beginning. “The majority of those known to have BoDV-1 initially suffered from headaches, fever and a general feeling of illness,” it says on an information page of the LGL. Only later did behavioral problems, speech and gait disorders and severe encephalitis develop. Of all the previously known ill people, only three survived “with the most serious consequential damage”.
Several projects are currently underway to get closer to the virus. Above all, Maitenbeth and its approximately 2000 inhabitants are the focus of research interest: The Friedrich Loeffler Institute as a federal research facility for animal health examines the local shrew population. At the end of July, the LGL and the University Hospital Regensburg asked volunteers to take blood and have a nasal swab in the multi-purpose hall. Among other things, the samples are examined for BoDV-1 antibodies, similar to what is known from Corona, in order to detect any unknown infections and to be able to draw conclusions about the spread of the virus. Results are expected in the fall.