Seroprevalence and Epidemiological Characteristics of Severe Fever with Thrombocytopenia Syndrome in Patients with Chronic Diseases in Korea

Severe fever with thrombocytopenia syndrome (SFTS) is a tick-borne disease with a high mortality rate. While research has focused on high-risk rural populations and healthy individuals in endemic regions, such as Jeju Island, data on patients with underlying chronic diseases remain limited. This study aimed to evaluate the seroprevalence of SFTS virus (SFTSV) in patients with various chronic diseases across the Republic of Korea. Serum samples (n = 2948) collected from 10 regional biobanks between 2009 and 2019 were analyzed using a double-antigen sandwich enzyme-linked immunosorbent assay. The overall seroprevalence was 1.22% (36/2948). Seropositivity was significantly higher in males (1.73%) than in females (0.73%, p = 0.013) and increased with age (p = 0.001), peaking at 2.73% in individuals aged 70–79. Geographically, the highest rates were in Gyeongbuk (3.03%), Jeonnam (2.40%), and Gangwon (1.83%). Multivariable logistic regression showed older age (adjusted odds ratio 1.47 per 10-year increase, 95% confidence interval: 1.12–1.97) as the strongest independent predictor of seropositivity. Patients with hepatobiliary/pancreatic cancer (3.16%) and prostate cancer (2.50%) exhibited higher seroprevalence than those in other disease groups. SFTSV exposure is non-negligible among those with chronic diseases, particularly older males in rural provinces. Public health strategies should specifically address these vulnerable populations.