Evolution and the potential for human-to-human transmission of severe fever with thrombocytopenia syndrome virus in low transmission settings in China.

Objective: Severe fever with thrombocytopenia syndrome (SFTS), an emerging infectious disease with substantial mortality, was first reported in China in 2009 and subsequently became endemic to South Korea, Japan, Vietnam, and the United Arab Emirates. Despite growing concerns about its transmission dynamics, the potential for human-to-human transmission through close physical contact remains inadequately explored in the literature. Methods: We conducted comprehensive epidemiological investigations of the initial cases of SFTS. In these investigations, real-time fluorescent reverse transcription polymerase chain reaction (RT-PCR) was used to analyze blood samples, followed by whole-genome sequencing (WGS) for phylogenetic tree construction. Results: Our analyses identified one potential index case (Case A) and one confirmed case (Case B), both of which tested positive for SFTS virus (SFTSV) nucleic acid. Notably, we observed an 8.65 % positive rate for SFTSV nucleic acid in Conclusions: Collectively, our study further demonstrated that close intimate contact may serve as a significant mode of SFTSV transmission among humans. This finding underscores the importance of enhancing awareness and implementing preventive measures among patients, healthcare providers, and relevant public health personnel regarding the human-to-human transmission of SFTS, contributing to more targeted public health strategies in SFTS-endemic regions, particularly in areas with low endemicity levels.