Severe fever with thrombocytopenia syndrome (SFTS) is an acute febrile illness characterized by fever, leukopenia, thrombocytopenia, and gastrointestinal symptoms such as diarrhea, nausea, and vomiting resulting from infection with the SFTS virus (SFTSV). The SFTSV is transmitted to humans by tick bites, primarily from Haemaphysalis longicornis, Amblyomma testudinarium, Ixodes nipponensis, and Rhipicephalus microplus. Human-to-human transmission has also been reported. Since the first report of an SFTS patient in China, the number of patients has also been increasing. The mortality rate of patients with SFTS remains high because the disease can quickly lead to death through multiple organ failure. In particular, an average fatality rate of approximately 20% has been reported for SFTS patients, and no treatment strategy has been established. Therefore, effective antiviral agents and vaccines are required. Here, we aim to review the epidemiology, clinical manifestations, laboratory diagnosis, and various specific treatments (i.e., antiviral agents, steroids, intravenous immunoglobulin, and plasma exchange) that have been tested to help to cope with the disease.

Severe fever with thrombocytopenia syndrome (SFTS) is emerging and the number of SFTS cases increased year by year in China. In order to explore the epidemiology trend, we analyzed the changing epidemiological characteristics of SFTS cases in different years and compare characteristics in different provinces. From 2011 to 2016, a total of 5360 laboratory-confirmed SFTS cases were reported and annual case numbers increased year by year. Most SFTS cases occurred in individuals aged between 40 years and 80 years (91.57%), but age distributions of SFTS cases in different years were significantly different and the median ages increased slightly year by year. The numbers of affected counties from 2011 to 2016 increased sharply from 98 to 167. Of note, the seasonal distributions of SFTS cases in different provinces were significantly different (Fisher = 712.157, P = 0.000) and provinces in south regions showed earlier epidemic peak and longer epidemics durations. The median time from illness onset to confirmation of different years was significantly different (χ2 = 896.088, P = 0.000) and it peaked in 2014. Furthermore, case fatality rate was associated with province, year, and age of SFTS cases. These results may be helpful for authorities to better preventive strategy and improve interventions against SFTS.

The growing epidemics of severe fever with thrombocytopenia syndrome (SFTS), an emerging tick-borne disease in East Asia, and its high case fatality rate have raised serious public health concerns.

With global warming and lush forest change, vector-borne infections are expected to increase in the number and diversity of agents. Since the first report of severe fever with thrombocytopenia syndrome (SFTS) in 2013, the number of reported cases has increased annually in South Korea. However, although tick-borne encephalitis virus (TBEV) was detected from ticks and wild rodents, there is no human TBE case report in South Korea. This study aimed to determine the seroprevalence of TBEV and SFTS virus (SFTSV) among forest and field workers in South Korea. From January 2017 to August 2018, a total 583 sera were obtained from the forest and field workers in South Korea. IgG enzyme-linked immunosorbent assay (ELISA) and neutralization assay were conducted for TBEV, and indirect immunofluorescence assay (IFA) and neutralization assay were performed for SFTSV. Seroprevalence of TBEV was 0.9% (5/583) by IgG ELISA, and 0.3% (2/583) by neutralization assay. Neutralizing antibody against TBEV was detected in a forest worker in Jeju (1:113) and Hongcheon (1:10). Only 1 (0.2%) forest worker in Yeongju was seropositive for SFTSV by IFA (1:2,048) and neutralizing antibody was detected also. In conclusion, this study shows that it is necessary to raise the awareness of physicians about TBEV infection and to make efforts to survey and diagnose vector-borne diseases in South Korea.

目的 研究湖北省随州市不同种属的蜱虫样本携带发热伴血小板减少综合征布尼亚病毒（severe fever with thrombocytopenia syndrome virus, SFTSV）情况，并探讨蜱虫与病例来源的病毒在分子进化水平上的亲缘关系。方法 于2016年、2017年连续2年在湖北省随州市采集蜱1 158只，收集该地区具有发热和血小板减少症状的病例血清样本86份，检测病毒核酸。将阳性标本采用Vero细胞开展病毒分离、测定分离到毒株的全基因组序列，并开展蜱虫和病例来源SFTSV病毒株的同源性比较和系统发生研究。结果 湖北省随州市长角血蜱、中华硬蜱和微小扇头蜱为优势种（95.34%）。根据蜱的种属和发育阶段合并样本，共得到832个合并样本，其中有4个检出SFTSV。该地区的总体最低感染率为0.35%。从长角血蜱中成功分离得到的1株SFTSV，命名为HB 2016-P35。该毒株与湖北省已报道的16株病例来源病毒具有较高的同源性，特别是与来自于同一地区的人源毒株HB 2017-49具有高度的同源性（基因组相似度99.9%）。此外，研究结果表明湖北省SFTSV病毒存在至少5个基因型，涵盖了几乎所有已报道的SFTSV基因型。结论 湖北省随州市蜱携带及传播SFTSV整体上处于较低水平。新分离自蜱虫的SFTSV毒株与周边病例携带病毒具有相似的基因型特征和较高的序列同源性。本研究结果提示蜱-人传播最有可能是人类感染SFTSV的途径，需持续在发热伴血小板减少综合征（severe fever with thrombocytopenia syndrome, SFTS）流行地区开展长期蜱虫携带SFTSV监测。

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging infectious disease that was caused by a novel bunyavirus, SFTSV. The study aimed to disclose the epidemiological and clinical characteristics of SFTSV infection in China so far. An integrated clinical database comprising 1920 SFTS patients was constructed by combining first-hand clinical information collected from SFTS sentinel hospitals (n = 1159) and extracted data (n = 761) from published literature. The considered variables comprised clinical manifestations, routine laboratory tests of acute infection, hospitalization duration and disease outcome. SFTSV-IgG data from 19 119 healthy subjects were extracted from the published papers. The key clinical variables, case-fatality rate (CFR) and seroprevalence were estimated by meta-analysis. The most commonly seen clinical manifestations of SFTSV infection were fever, anorexia, myalgia, chill and lymphadenopathy. The major laboratory findings were elevated lactate dehydrogenase, aminotransferase, followed by thrombocytopenia, lymphocytopenia, elevated alanine transaminase and creatine kinase. A CFR of 12·2% was estimated, significantly higher than that obtained from national reporting data, but showing no geographical difference. In our paper, the mortality rate was about 1·9 parts per million. Older age and longer delay to hospitalization were significantly associated with fatal outcome. A pooled seroprevalence of 3·0% was obtained, which increased with age, while comparable for gender. This study represents a clinical characterization on the largest group of SFTS patients up to now. A higher than expected CFR was obtained. A wider spectrum of clinical index was suggested to be used to identify SFTSV infection, while the useful predictor for fatal outcome was found to be restricted.