Borna disease virus (BDV) has gained lot of interest because of its zoonotic potential, ability to introduce cDNA of its RNA transcripts into host genomes, and ability to cause severe neurobehavioural diseases. Classical Borna disease is a progressive meningoencephalomyelitis in horses and sheep known in central Europe for centuries. According to current knowledge BDV or its close relative infects also several other species, including at least occasionally humans, in central Europe and elsewhere, but the existence of potential ‘human Borna disease’ with its suspected neuropsychiatric symptoms is highly controversial.
Recent detection of endogenised BDV genes in primates and various other vertebrate genomes confirms that at least the ancient bornaviruses viruses infected our ancestors. The epidemiology of BDV is largely unknown, but accumulating evidence indicates vectors and reservoirs among small wild mammals. The aim of this review is to bring together the current knowledge on epidemiology of BDV infections, specifically, geographic and host distribution, and salient clinical aspects.