Epidemiological and Clinical Feature of Severe Fever with Thrombocytopenia Syndrome in South Korea, 2013-2015

Abstract

Introduction Severe fever with thrombocytopenia syndrome (SFTS) is an emerging infectious disease, which is endemic in China, South Korea and Japan. The case-fatality of SFTS is high, but the literature for SFTS outside China is small. The object of the study was to evaluate the overall characteristics of SFTS in South Korea since its first report in 2013. Methods The subjects were all SFTS patients reported to the Korea Centers for Disease Control and Prevention from 2013 to 2015 who were confirmed either genotypic or serologic methods. Nationwide SFTS Clinical Network was formed and retrospectively collected clinical information. The epidemiologic and clinical characteristics of SFTS were analyzed, and risk factors leading to the death of SFTS patients were sought. Results Total 172 SFTS patients were confirmed for three years in South Korea. Two patients were confirmed outside a reference laboratory. SFTS occurred all over the country except for urban areas, but hilly area in eastern and southeastern region, and Jeju island (incidence, 1.26 cases /105 people) were major endemic areas. The yearly incidence increased from 36 cases in 2013 to 81 cases in 2015. The main epidemic season was from May to October. The overall case-fatality was 32.6%. The clinical manifestations were similar to known three phases of febrile, multi-organ dysfunctions, and convalescence. Confusion, the elevation of C-reactive protein, and the prolongation of activated partial thromboplastin time were associated with the death of SFTS patients. Two outbreaks of nosocomial SFTS transmission involving nine healthcare workers during emergency care were observed.

Conclusions SFTS is an endemic disease in South Korea, with a nationwide distribution and a high case-fatality ratio. Confusion, elevated levels of C-reactive protein, and prolonged activated partial thromboplastin times were associated with mortality in patients with SFTS.