Severe fever with thrombocytopenia syndrome (SFTS), a tickborne viral disease, has been identified in China, South Korea, and Japan since 2009. We found retrospective evidence of SFTS virus (SFTSV) infection in Vietnam, which suggests that SFTSV infections also occur in Vietnam, where the virus has not been known to be endemic.

Serologic and molecular surveillance of serum collected from 152 suspected scrub typhus patients in Myanmar revealed Orientia tsutsugamushi of genotypic heterogeneity. In addition, potential co-infection with severe fever with thrombocytopenia syndrome virus was observed in 5 (3.3%) patients. Both scrub typhus and severe fever with thrombocytopenia syndrome are endemic in Myanmar.

Severe fever with thrombocytopenia syndrome (SFTS) is a tick-borne viral disease. The SFTS virus (SFTSV) has been detected in the Haemaphysalis longicornis, which acts as a transmission host between animals and humans. SFTSV was first confirmed in China in 2009 and has also been circulating in Japan and South Korea. However, it is not known if a genetic connection exists between the viruses in these regions and, if so, how SFTSV is transmitted across China, South Korea, and Japan. We therefore hypothesize that the SFTSV in South Korea share common phylogenetic origins with samples from China and Japan. Further, we postulate that migratory birds, well-known carriers of the tick H. longicornis, are a potential source of SFTSV transmission across countries. Our phylogenetic analysis results show that the SFTSV isolates in South Korea were similar to isolates from Japan and China. We connect this with previous work showing that SFTSV-infected H. longicornis were found in China, South Korea, and Japan. In addition, H. longicornis were found on migratory birds. The migratory bird routes and the distribution of H. longicornis are concurrent with the occurrence of SFTSV. Therefore, we suggest that migratory birds play an important role in dispersing H. longicornis-borne SFTSV.

Severe fever with thrombocytopenia syndrome (SFTS) was reported in China in 2009 and in South Korea in 2012. We found retrospective evidence of SFTS virus infection in South Korea in 2010, suggesting that infections in South Korea occurred before previously reported and were more concurrent with those in China.

Severe fever with thrombocytopenia syndrome virus (SFTSV) and severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) can cause the hyperproduction of inflammatory cytokines, which have pathological effects in patient including severe or fatal cytokine storms. To characterize the effect of SFTSV and SARS‐CoV‐2 infection on the production of cytokines in severe fever with thrombocytopenia syndrome (SFTS) and COVID‐19 patients, we performed an analysis of cytokines in SFTS and COVID‐19 patients and also investigated the role of interleukin‐10 (IL‐10) in vitro studies: lipopolysaccharide‐induced THP‐1‐derived macrophages, SFTSV infection of THP‐1 cells, and SARS‐CoV‐2 infection of THP‐1 cells. In this study, we found that levels of both IL‐10 and IL‐6 were significantly elevated, the level of transforming growth factor‐β (TGF‐β) was significantly decreased and IL‐10 was elevated earlier than IL‐6 in severe and critical COVID‐19 and fatal SFTS patients, and inhibition of IL‐10 signaling decreased the production of IL‐6 and elevated that of TGF‐β. Therefore, the hyperproduction of IL‐10 and IL‐6 and the low production of TGF‐β have been linked to cytokine storm‐induced mortality in fatal SFTS and severe and critically ill COVID‐19 patients and that IL‐10 can play an important role in the host immune response to severe and critical SARS‐CoV‐2 and fatal SFTSV infection.

Severe fever with thrombocytopenia syndrome (SFTS) is tick-borne viral disease that was first suspected in China in 2009. The causative virus (SFTSV) was isolated in 2009 and reported in 2011, and SFTSV expanded its geographic distribution in 2012–2013, from China to South Korea and Japan. Most SFTSV infections occur through Haemaphysalis longicornis. However, SFTSV infection can also occur between family members, and nosocomial transmission of SFTSV is also possible through close contact with a patient. In this study, we first analyzed clinical, epidemiological, and laboratory data for SFTS patients and family members of an index patient in Korea. The S segment of SFTSV was amplified from the sera of three patients, and the S segment of SFTSV and IgG specific to SFTSV were detected in the serum from one family member; although this individual had no history of exposure to H. longicornis, she frequently had close contact with the index patient. In Korea, SFTSV infection among family members does not have to be reported, and we suggest that person-to-person transmission of SFTSV among family members is possible in Korea.