Neurotropic Tick-Borne Flavivirus in Alpine Chamois (), Austria, 2017, Italy, 2023.

The European subtype of tick-borne encephalitis virus (TBEV-Eur; species , family ) was the only tick-borne flavivirus present in central Europe known to cause neurologic disease in humans and several animal species. Here, we report a tick-borne flavivirus isolated from Alpine chamois () with encephalitis and attached ticks, present over a wide area in the Alps. Cases were detected in 2017 in Salzburg, Austria, and 2023 in Lombardy and Piedmont, Italy. The virus strains exhibit 94.8-97.3% nucleotide identities to each other and are more closely related to Louping ill viruses (LIV; ; 90-92% identities) than to TBEV-Eur (less than 88%). The chamois-derived virus strains, tentatively termed "Alpine chamois encephalitis virus", form a well-supported independent genetic clade with Spanish goat encephalitis virus, clearly separated from other LIV. This supports its designation as a new virus subtype with the proposed shared taxonomic name "Spanish goat and Alpine chamois encephalitis virus subtype" within the species . The zoonotic potential of this newly identified virus subtype as well as its host range in other animal species including farm animals needs to be further investigated.