Secondary transmission of severe fever with thrombocytopenia syndrome in a hospital setting in Republic of Korea: a retrospective observational study of personal protective equipment use and infection risk factors

Objectives: This study investigated a cluster of secondary human-to-human transmission of severe fever with thrombocytopenia syndrome (SFTS) in a hospital setting, focusing on infection risk factors and the role of personal protective equipment (PPE). Methods: A descriptive epidemiological investigation was conducted following the death of an index patient with laboratory-confirmed SFTS. A total of 27 close contacts, including healthcare workers and a funeral director, were monitored for symptoms. Suspected cases underwent real-time reverse transcription polymerase chain reaction testing. Clinical features, PPE use, and exposure histories were analyzed. The Fisher exact test was used to assess associations between PPE use and infection. Viral genotyping and sequence analyses were performed to evaluate transmission routes. Results: The index patient deteriorated rapidly and died after repeated cardiopulmonary resuscitation (CPR), during which 8 secondary cases occurred. Most infections were identified among individuals involved in CPR or postmortem care without adequate PPE. Although not statistically significant, infection rates were higher among those who did not wear masks or who used low-filtration masks. Proper use of gloves, gowns, and goggles was associated with lower infection rates. Cycle threshold values in secondary cases (range, 34-39) were higher than in the index case (14.07), suggesting lower viral loads. Sequence analysis demonstrated 99.6%-100% homology between the index and secondary cases; all isolates were genotype B, indicating direct transmission. Conclusion: This study provides molecular and epidemiological evidence of nosocomial SFTS transmission. Inadequate PPE use during aerosol-generating procedures likely facilitated infection, underscoring the importance of strict adherence to PPE protocols and reinforced infection control practices.