Epidemiological characteristics of patients with severe fever with thrombocytopenia syndrome in Republic of Korea in 2017

Seo Choong Won, Kim Jeong Hyun, Kim Eun Young, Lee Seung Eun, Park Hye Kyung
Division of Infectious Disease Surveillance, Center for Control of Infectious Diseases, KCDC

Background: The nationwide surveillance for severe fever with thrombocytopenia syndrome (SFTS) was initiated in 2013 in the Republic of Korea. SFTS is an emerging tick-borne disease characterized by fever, thrombocytopenia and gastrointestinal symptoms including diarrhea, abdominal pain and vomiting. We analyzed the epidemiological and clinical features of reported SFTS cases in 2017.
Methods/Results: A total of 272 cases were analyzed: 270 were laboratory-confirmed cases and 2 were suspect cases. There were 54 deaths (Case Fatality Rate, CFR: 19.9%) and the majority of cases were reported from May to November. The peak of cases were observed in October with 79. The age distribution of cases ranged between 19 and 91 years (median 66 years). 253 (93.0%) cases were aged more than 50 years and 118 (43.4%) cases were farm workers. Geographically, cases were mainly reported in Gyeonggi, Gangwon, Gyeongbuk, Chungnam, and Jeju provinces. In terms of risk behaviors, 197 cases (72.4%) had history of outdoor activities including farmworks.
Conclusion: Age and neurologic symptoms including decreased level of consciousness, slurred speech and convulsions were markedly associated with SFTS-related mortality. The risk of death was 6.931 (95% CI=2.217-22.579) times higher among the cases with neurological symptoms than among the cases without ones. Those who experience symptoms after outdoor activities such as fever, gastrointestinal symptoms are advised to receive early diagnosis and proper treatment.

Keywords: Severe fever with thrombocytopenia syndrome, Farm workers, Thrombocytopenia, Fever, Gastrointestinal symptoms