Cluster investigation report: a probable urine-associated transmission event of severe fever with thrombocytopenia syndrome-a case report.

Introduction: Severe fever with thrombocytopenia syndrome (SFTS) is an emerging tick-borne viral disease with a high case fatality rate. Human-to-human transmission has been increasingly documented, primarily through direct contact with blood or bloody secretions. On June 21, 2025, a case of SFTS was reported in Zhumadian City, Henan Province. On July 3, a second case-epidemiologically linked to the first-was reported to the local Centers for Disease Control (CDC) through the notifiable disease reporting system, following laboratory confirmation on July 1. Case presentation: A 77-year-old female farmer with underlying comorbidities was hospitalized with fever, leukopenia, and thrombocytopenia, and subsequently died of SFTS. Her 31-year-old granddaughter, who had an open wound on her hand, cared for the patient and cleaned her urine. Eleven days later, she developed fever, nausea, vomiting, headache, fatigue, and myalgia. Laboratory tests confirmed SFTS virus infection by RT-PCR, with an initial cycle threshold (Ct) value of 38.85, which subsequently decreased to 31.48 over the following 2 days, indicating active viral replication. She recovered after antiviral therapy and was discharged on July 7. Comprehensive epidemiological investigation ruled out other potential transmission routes, including blood contact, tick bites, and environmental exposure. However, direct virological evidence from the index patient's urine and genomic sequencing to confirm viral homology between the two cases were not available. Conclusion: This report describes a probable human-to-human SFTS transmission event associated with urine exposure through an open wound. While the absence of direct virological and genomic evidence precludes definitive confirmation, the convergence of epidemiological, clinical, and temporal evidence strongly supports this transmission route. This case highlights the need for enhanced protective measures-particularly the use of gloves when handling any body fluids, including urine-during care of SFTS patients.