One-year mortality and morbidities of severe fever with thrombocytopenia syndrome compared with other diseases: A nationwide cohort study in South Korea

Background: The long-term mortality and morbidity of patients with severe fever with thrombocytopenia syndrome (SFTS) remain unclear. Methods: This retrospective cohort study was conducted using the National Health Insurance Service dataset on hospitalized patients with SFTS aged ≥20 years between 2016 and 2021 (n = 1,217). Each SFTS case was matched with three controls hospitalized for non-SFTS-related diseases using propensity score matching. The all-cause mortality of patients with SFTS was evaluated during the one-year follow-up and compared with that of controls. Post-discharge events were investigated to determine the effects of SFTS on post-acute sequelae. Results: Finally, 1,105 patients with SFTS and 3,315 controls were included. Patients with SFTS had a higher risk of death during the one-year follow-up than that of controls (hazard ratio [HR], 2·26; 95% confidence interval [CI], 1·82–2·81). Thirty-day mortality was significantly higher in the SFTS group (HR, 3·99; 95% CI, 3·07–5·19) than in the control group. An increased risk of death after 31–365 days was observed among controls, though this difference was significant only among patients in their 80s (HR, 0·18; 95% CI, 0·06–0·57). For post-discharge events, patients in the SFTS group exhibited a higher risk of readmission (HR, 1·17; 95% CI, 1·04–1·32) and emergency room visit (HR, 2·32; 95% CI, 1·96–2·76) than those in the control group. Conclusion: SFTS induces a higher risk of short-term mortality and post-acute sequelae in hospitalized patients during a one-year follow-up than non-SFTS-related diseases. Our results provide guidance for the management of SFTS. Author summary: Severe fever with thrombocytopenia syndrome (SFTS) is a life-threatening viral disease, which has expanded beyond Asian countries. However, most studies have focused on the short-term mortality of patients with SFTS, and knowledge of their long-term outcomes is limited. This nationwide cohort study evaluated long-term outcomes of hospitalized patients with SFTS between 2016 and 2021 using the national dataset. We found that hospitalized patients with SFTS had higher one-year mortality (HR, 2.26) than those without SFTS. An increased mortality risk was attributed to death in the first 30 days of hospitalisation (HR, 3.99). Although the long-term mortality (31–365 days) did not differ between patients with and without SFTS, except for those in their 80s, patients with SFTS suffered from post-acute events, including readmission (HR, 1.17) or emergency room visit (HR, 2.32) during the one-year follow-up. SFTS is an emerging infectious disease that demands attention. The disease burden extends beyond the acute phase, with patients often experiencing ongoing health problems even after hospital discharge. Our findings underscore the post-acute burden of SFTS and offer valuable insights for the development of effective management plans for acute and post-acute illnesses in patients with SFTS.