June 6, 2025, 10:37 am | Read time: 6 minutes
Fever, headaches, and a general feeling of illness—initially, the symptoms of a Bornavirus infection resemble those of a common cold. But appearances can be deceiving. Within a few days, those affected can develop severe encephalitis, which can be fatal in the worst cases. Recently, two men contracted the rare Bornavirus—one has since died, and the other is in intensive care. FITBOOK editor Julia Freiberger explains how dangerous the virus is.
A mysterious pathogen, little-known transmission routes, and a high mortality rate: The Bornavirus (BoDV-) raises many questions despite scientific advances. Although infections in humans are extremely rare, recent cases from Bavaria show how serious the threat is—especially in certain risk areas.1
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Overview
What is the Bornavirus?
The Borna Disease Virus 1 (BoDV-1), also known as the “classic Bornavirus,” is a virus originally known only in animals—especially horses and sheep, which became severely ill from it. The disease was first described in the 18th century and was named after the town of Borna in Saxony, where a mass die-off of horses occurred in 1885.
For a long time, BoDV-1 was considered exclusively an animal disease. It wasn’t until 2018 that researchers discovered the virus could also cause severe brain inflammation—known as encephalitis—in humans. Since then, it has been classified as a zoonosis: a disease that can be transmitted from animals to humans.
Particularly insidious: There is still no targeted treatment or vaccine for the infection. The disease is fatal in most cases. Only a few affected individuals have survived—sometimes with severe lasting damage.2
Distinction from the Squirrel Bornavirus
In addition to the classic Bornavirus (BoDV-1), there is a second variant that can also be dangerous to humans: the so-called Squirrel Bornavirus (VSBV-1). This virus has been found in exotic squirrel species—mostly in animals kept as pets in Europe. VSBV-1 can also cause fatal brain inflammation in humans, but it has a different origin and is very rare. In contrast, BoDV-1 is widespread in the native environment—especially in southern and eastern Germany.3
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Field Shrew as a Carrier
The field shrew is the only known animal that permanently carries the Bornavirus without becoming ill itself. It can transmit the virus through saliva, feces, urine, and even its skin—thus infecting its surroundings unnoticed.
The animals mostly live in rural areas, rarely leave their territory, and are particularly common in certain regions of Germany—especially in Bavaria, Saxony, Thuringia, Saxony-Anhalt, and Baden-Württemberg. The virus has also been detected in neighboring countries like Austria and Switzerland. In other parts of Europe, it has not yet been found in humans.
How One Can Get Infected with the Pathogen
Despite intensive research, it is not precisely clear how the virus is transmitted from the shrew to humans. Possible infection routes include:
- inhaling contaminated dust (such as during gardening or in a shed),
- contact with contaminated soil, water, or food,
- or through a direct bite from a shrew.
Even if pets like cats hunt shrews, this could be an indirect transmission route—though this has not been proven. Human-to-human transmission is not known, except for isolated cases related to organ transplants.4
Symptoms Initially Flu-like
The infection often begins mildly: fever, headaches, and a general feeling of illness. However, within a few days, the condition rapidly worsens. Typical subsequent symptoms include:
- speech disorders
- unsteady gait
- noticeable personality changes
- seizures
As the disease progresses, severe brain inflammation occurs. Within a few days to weeks, it is possible for affected individuals to fall into a coma. Without treatment, the infection is fatal.
How Common is a Bornavirus Infection?
According to the Robert Koch Institute (RKI), BoDV-1 infection is one of the rarest diseases in Germany. Approximately five to ten acute cases are reported each year. For comparison: about 200 people are struck by lightning annually—a BoDV-1 disease is thus extremely rare. The RKI does not suspect a high number of unreported cases.5
Most known cases have occurred in rural areas of Bavaria. Although no human infections have been detected in other European countries, experts believe the virus could theoretically become dangerous anywhere it occurs in field shrew populations.
Two Infection Cases in Pfaffenhofen
Even isolated cases can have dramatic outcomes, as shown by the example from Pfaffenhofen in Upper Bavaria. There, two men independently contracted the virus a few days ago—one of them died, and the other is hospitalized. The exact transmission route remains unclear.
How Can the Virus Be Detected?
A Bornavirus infection is difficult to recognize because the initial symptoms like fever, headaches, or exhaustion are very general—they resemble many other, harmless diseases. Only when additional noticeable symptoms such as speech problems, unsteady walking, or unusual behavior occur do doctors consider rarer causes like BoDV-1.
A suspected case—such as unexplained brain inflammation in a person from a known risk area—is investigated through special lab tests. Essentially, two methods are used:
- Antibody detection: If the immune system has already dealt with the virus, specific antibodies can be detected in the blood or cerebrospinal fluid. This examination is the most important component for diagnosis in living patients.
- PCR test: This detects the virus’s genetic material—either in cerebrospinal fluid, obtained through a lumbar puncture, or in brain tissue. The latter is only possible post mortem. This method is particularly reliable but technically demanding.
Since March 1, 2020, Bornavirus infections in humans must be officially reported in Germany. If the virus is detected in the lab, the health department must be informed immediately—so cases can be recorded nationwide and better monitored.6
Protective Measures: How to Protect Yourself from the Bornavirus
Even though the risk of contracting the Bornavirus is very low, a cautious approach to potential transmission sources is worthwhile, especially in affected regions—particularly when working outdoors or in rural areas.
To minimize the risk, the following behavioral rules should be observed:
- Avoid shrews and their droppings, especially during gardening or cleaning work, in sheds, attics, or near compost.
- Do not touch dead animals directly—wearing gloves is mandatory.
- Before disposing of dead shrews or their excretions, spray them thoroughly with a cleaning agent. This prevents potentially contaminated dust from entering the air.
- Take appropriate precautions when disposing: gloves, a close-fitting mask (such as FFP2 or FFP3), and, if necessary, protective goggles can provide additional protection.
- Pick up the animal body with a plastic bag, seal it well, and dispose of it with household waste.
- After exposure to dusty work, shower thoroughly, wash hair, and put clothes directly in the laundry.
These simple measures help effectively prevent possible virus transmission to humans—even though the overall risk is very low.
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Research and Education: Many Open Questions
Despite many insights, there are still open questions about the Bornavirus—such as how exactly humans become infected and why so few cases occur. Researchers in Germany continue to investigate possible transmission routes and risk factors. Veterinarians are also important: unusual disease courses in animals should be reported to gather further clues. In affected regions, health departments provide online information about protective measures and sometimes offer consultations where questions can be answered directly.