Epidemiological and etiological investigation of a rare family cluster caused by SFTS in Anhui Province in 2023

Abstract Background Severe fever with thrombocytopenia syndrome (SFTS) is an emerging tick-borne infectious disease discovered in the 21st century. Transmission of the disease among humans has been described, but the transmission mechanisms still need further study. Methods Epidemiologic investigations were conducted after a cluster of 18 cases of SFTSV in November 2023 and 4 of them died. The index patient experienced onset of SFTSV on 21 October and died on 2 November. The secondary cases had onset from 7 to 13 November, peaking on 10 November. Results According to epidemiologic investigations, 14 secondary cases contracted the disease through contact with blood of the index patient. Another 3 secondary patients did not have a history of contact with the blood of the index patient, but they stayed in the mourning hall for a while. The index patient worked as a powerful source to spread virus to people having close contact with him. Meanwhile, the evidence of aerosol transmission of SFTSV can also be found in this cluster. Risk factors assessment revealed that exposure to the blood of a deceased person during burial preparation was more likely to produce secondary cases than exposure to the blood of living patient. Conclusions Contacting with deceased blood during funeral was associated with secondary cases of SFTS.