Seasonal dynamics of hedgehog-borne ticks and severe fever with thrombocytopenia syndrome virus in Beijing's urban parks.

Severe fever with thrombocytopenia syndrome virus (SFTSV), an emerging tick-borne pathogen, has caused a rising number of human cases in the urban-rural fringe of Beijing since 2021. This study explores the seasonal dynamics of hedgehog-associated ticks and SFTSV transmission in urban parks of Beijing. Surveys across six parks revealed distinct activity patterns: adult Haemaphysalis longicornis peaked in summer, while nymphs dominated spring and autumn. All collected H. longicornis belonged to parthenogenetic populations. A near-complete SFTSV genome (C4 strain) was identified in a tick collected from Taoranting Park, suggesting multiple viral introductions into Beijing. Serological analysis showed that > 50% of hedgehogs carried SFTSV-neutralizing antibodies in spring; yet seropositivity declined markedly in summer and autumn, indicating recurrent infections and implicating hedgehogs as potential reservoirs. These findings reveal an urban SFTSV transmission cycle maintained by hedgehogs and parthenogenetic H. longicornis, emphasizing the urgency of enhanced surveillance and public health interventions to curb urban zoonotic risks.