A cluster of severe fever with thrombocytopenia syndrome with household and nosocomial transmission in Zhejiang Province, China, 2023.

BACKGROUND: Severe fever with thrombocytopenia syndrome (SFTS) is an emerging infectious disease caused by the SFTS virus (SFTSV). It is primarily transmitted by tick bites, and person-to-person transmission can occur through direct contact with the blood or blood-contaminated secretions of patients. We analyzed and discussed the transmission routes of a cluster of SFTS involving both household and nosocomial transmission, providing foundational data for the prevention and control of SFTS. METHODS: We investigated a cluster of SFTS cases in Zhejiang Province, China, in April 2023. Epidemiological, clinical, and entomological data were collected and analyzed. Genetic sequencing was used to confirm SFTSV infection and identify the source of the outbreak. RESULTS: Eight cases were identified, including one index case and seven secondary infections among the family members and healthcare workers (HCWs). The index patient, an 82-year-old female, likely contracted SFTSV from tick bites in her tea plantation. Direct contact with the patient’s blood led to secondary infections. 7 of the 12 individuals with direct blood contact developed SFTS, which was significantly different from that of individuals without direct blood contact (P = 0.01). Genetic analysis confirmed high homology between SFTSV sequences from patients and ticks. CONCLUSIONS: We demonstrated that the transmission routes of this SFTS cluster originated from a fatally ill patient infected through tick bites, and subsequently spread to family members and healthcare workers via blood contact. Enhanced infection control measures and early diagnosis are crucial.