Wild Mice and Shrews as Natural Reservoirs of Emerging Tickborne Yezo Virus, Hokkaido, Japan, 2023–2025

We screened 420 wild small mammals and 2,273 ticks for infections with an emerging tickborne orthonairovirus, Yezo virus, during 2023–2025 in Hokkaido, Japan. We detected virus in mice, shrews, and ticks that were closely related. Apodemus spp. mice and Sorex spp. shrews were identified as potent natural reservoirs of Yezo virus.