Infectious Disease · Public Health · 1 h ago
Wild mice and shrews identified as Yezo virus reservoirs in Hokkaido
A study in Hokkaido, Japan, screened 420 wild small mammals and 2,273 ticks collected or sampled during 2023–2025 for Yezo virus. Viral RNA was detected in mice and shrews, but not in voles; related virus sequences were also found in tick pools.
- YEZV RNA was detected in mice and shrews, not voles.
- Five positive shrews carried all three viral genome segments.
- Seven of 288 pooled tick samples tested positive.
- The early-release study was conducted in Hokkaido, Japan.
Researchers screened 420 wild small mammals captured at 14 sites in Hokkaido during 2023 and 2025. The sample included 252 mice, 121 voles and 47 shrews. They tested liver samples for Yezo virus (YEZV) RNA and serum from 199 animals for antibodies. In 2025, they also tested 288 pooled samples comprising 2,273 ticks collected at the same sites.
YEZV RNA was detected in 16 mammals: mice and shrews, while all voles tested negative. Five shrews were positive for all three viral genome segments. Infectious virus was isolated from one mouse and one shrew. Antibodies were found in 14 of 199 animals (7.0%). Seven tick pools tested positive for YEZV RNA. Viral sequences from mammals and ticks were closely related to previously reported sequences from human cases and other sources.
The findings support a role for Apodemus mice and Sorex shrews as natural YEZV reservoirs and suggest local circulation involving ticks. The study does not establish how often these animals transmit virus to ticks or how much they contribute to human infection. Sampling was limited to Hokkaido, and the article is an early release version that may change before final publication.
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Emerging Infectious Diseases: Wild Mice and Shrews as Natural Reservoirs of Emerging Tickborne Yezo Virus, Hokkaido, Japan, 2023–2025 ↗This is an automated AI-condensed summary that has not yet been reviewed by an editor. Always consult the full item at the original source.