Severe Fever with Thrombocytopenia Syndrome in South Korea, 2013-2015

BackgroundSevere fever with thrombocytopenia syndrome (SFTS) is an emerging infectious disease that was recently identified in China, South Korea and Japan. The objective of the study was to evaluate the epidemiologic and clinical characteristics of SFTS in South Korea.Methods/Principal FindingsSFTS is a reportable disease in South Korea. We included all SFTS cases reported to the Korea Centers for Disease Control and Prevention (KCDC) from January 2013 to December 2015. Clinical information was gathered by reviewing medical records, and epidemiologic characteristics were analyzed using both KCDC surveillance data and patient medical records. Risk factors for mortality in patients with SFTS were assessed. A total of 172 SFTS cases were reported during the study period. SFTS occurred throughout the country, except in urban areas. Hilly areas in the eastern and southeastern regions and Jeju island (incidence, 1.26 cases /105 person-years) were the main endemic areas. The yearly incidence increased from 36 cases in 2013 to 81 cases in 2015. Most cases occurred from May to October. The overall case fatality ratio was 32.6%. The clinical progression was similar to the 3 phases reported in China: fever, multi-organ dysfunction, and convalescence. Confusion, elevated C-reactive protein, and prolonged activated partial thromboplastin times were associated with mortality in patients with SFTS. Two outbreaks of nosocomial SFTS transmission were observed.ConclusionsSFTS 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.背景：发热伴血小板减少综合征（Severe fever with thrombocytopenia syndrome, SFTS）是近年在中国、韩国及日本发现的一种新发传染病。本研究旨在评估韩国境内发热伴血小板减少综合征的流行病学与临床特征。 方法与主要结果：发热伴血小板减少综合征在韩国属于法定报告传染病。本研究纳入了2013年1月至2015年12月期间上报至韩国疾病控制与预防中心（Korea Centers for Disease Control and Prevention, KCDC）的所有发热伴血小板减少综合征病例。通过查阅病历收集临床信息，结合韩国疾病控制与预防中心监测数据与患者病历分析流行病学特征，并评估了发热伴血小板减少综合征患者死亡的危险因素。研究期间共上报172例发热伴血小板减少综合征病例。该病在韩国全域均有分布，仅城市地区未见病例。韩国东部、东南部丘陵地带及济州岛（发病率：1.26例/10万人年）为主要流行区。年发病率从2013年的36例升至2015年的81例，多数病例集中于5月至10月。整体病死率为32.6%。临床病程与中国报告的3个阶段相似：发热期、多器官功能障碍期及恢复期。意识障碍、C反应蛋白（C-reactive protein）升高及活化部分凝血活酶时间（activated partial thromboplastin times）延长与发热伴血小板减少综合征患者的死亡风险相关。本研究还观察到2起医院内发热伴血小板减少综合征传播暴发事件。 结论：发热伴血小板减少综合征在韩国为地方性流行传染病，呈全国性分布且病死率较高。意识障碍、C反应蛋白水平升高及活化部分凝血活酶时间延长与发热伴血小板减少综合征患者的死亡风险相关。