The Borna virus claimed its first known human victim in Germany in 1999, with a total of eight fatalities reported to date. Though the number appears low, recent research underscores the virus's controversy and elusive nature.
Borna disease virus (bornavirus) typically starts with fever and headache, progressing to encephalitis. In severe cases, patients experience memory loss, progressive loss of consciousness, gait disturbances, and seizures. The virus is named after Borna, a town in Saxony, Germany, where it first devastated horses in 1885.
Today, the bicolored white-toothed shrew (Crocidura leucodon) is the primary reservoir. Yet, human transmission pathways are not well defined. A landmark study from Germany, published in The Lancet Infectious Diseases on January 7, 2020, shed new light on this.
The research identified Borna disease in eight fatal cases from 1999 to 2019 among 56 encephalitis patients where initial causes were unidentified. Post-mortem brain tissue analysis confirmed the diagnosis, with deaths occurring 16 to 57 days after hospital admission.
Investigators gathered lifestyle data on 14 of the 56 patients. Many lived rurally, worked outdoors as farmers, or had frequent animal contact. Some encountered cats carrying shrews as prey.
Sequencing of the BoDV-1 bornavirus from the eight deceased revealed distinct strains, sometimes matching those in local sheep or horses. This indicated independent infections, not a single outbreak.
Despite few victims and unclear transmission, Borna virus has been detected in humans in the US and Japan. Decades of research were stalled by uncertainty over its zoonotic potential.
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