Epidemiological and clinical features of laboratory-diagnosed severe fever with thrombocytopenia syndrome in China, 2011–17: a prospective observational study

Summary Background Severe fever with thrombocytopenia syndrome (SFTS) is an emerging infectious disease with an increasing case number and extensive geographical expansion, raising concerns locally and globally; however, the description of its clinical features needs to be addressed by large studies. We aimed to determine all the clinical features of SFTS in a large population of patients in an endemic area. Methods In this prospective observational study, data were collected on patients admitted to the People's Liberation Army Hospital in Xinyang, Henan Province, China, with laboratory-diagnosed SFTS. Demographic, clinical, laboratory, and treatment data were collected for each patient, and patients were followed up within 2 weeks after discharge or discontinuation of treatment. The association between each demographic, clinical, and laboratory variable with a fatal outcome was assessed. A clinical scoring model was designed for the early prediction of a fatal outcome, and the effect of treatment on outcome was analysed. Findings Between April 1, 2011, and Oct 31, 2017, 2096 patients with laboratory-confirmed SFTS were admitted. Mean age at admission was 61·4 years (SD 12·2) and 1239 (59%) patients were female. The case fatality rate (CFR) was 16·2% (95% CI 14·6–17·8). A higher risk was associated with being male (unadjusted odds ratio [OR] 1·45, 95% CI 1·15–1·83; p=0·002), older age (for a 10-year increase, unadjusted OR 1·82, 95% CI 1·62–2·04; p 6 copies per mL (hazard ratio 9·72, 95% CI 1·30–72·87; p=0·027). Interpretation The changing epidemiological features and high CFR of SFTS underscore the necessity of continued surveillance. Early prediction of fatal outcome can be attained by monitoring of clinical and laboratory data. Ribavirin should be applied early, with best results achieved before the viral load reaches 1 × 10 6 copies per mL. Funding National Natural Science Foundation of China.