Emerging Multi-Source Transmission of SFTS Virus on a Remote Japanese Island: A One-Health Perspective

Tick-borne viral infections, including Severe Fever with Thrombocytopenia Syndrome (SFTS), pose a growing global public health threat owing to their potential for rapid spread and high mortality rates. We report a localized outbreak of SFTS virus (SFTSV) affecting both humans and cats on a remote island in Nagasaki, Japan, between April and May 20xx, comprising four feline and four human cases. Notably, no direct contact was observed between cats and humans. Four animals and one patient succumbed to the illness. Genomic analyses, conducted in collaboration with local health authorities, revealed a high similarity to previously reported strains in Nagasaki. Haplotype network analysis suggested multiple sources and complex transmission pathways with evidence of diverse viral introduction events. The inconsistency across viral segments underscores the complexity of virus circulation. This outbreak underscores the critical importance of a One Health approach—integrating human, animal, and vector surveillance—to effectively monitor, understand, and mitigate the public health impact of tick-borne viruses, which are an increasingly significant threat in endemic and emerging regions worldwide.