Risk factors for person-to-person transmission of severe fever with thrombocytopenia syndrome

Objective: To determine the risk factors for person-to-person transmission of severe fever with thrombocytopenia syndrome (SFTS). Design: Studies reporting the person-to-person transmission or cluster infection of SFTS were identified and included for risk-factor analyses. Methods: Risk factors were investigated by analyzing characteristics of index patients who caused cluster infection and correlation between exposure history and secondary infection. Results: Analyses of 23 clusters of SFTS infections indicated that all index patients died and that they all had a symptom of bleeding 24 hours before death. Of 89 secondary cases, 82% had been exposed to the index patients' blood. The blood-contact-specific secondary attack rate was 62.4% (73 of 117). The risk relative value was 25 (95% CI, 15-42); thus, the probability of a person getting infected was 25 times more likely when they had contacted blood than when they had not. Conclusion: Exposure to blood of SFTS patients is the highest risk factor for person-to-person infection with SFTSV. SFTS patients' families and healthcare workers should be educated to handle SFTS patients properly and safely to prevent the spread of SFTSV.