Effect of Severe Fever With Thrombocytopenia Syndrome Virus Genotype on Disease Severity, Viral Load, and Cytokines in South Korea

Abstract

Background Severe fever with thrombocytopenia syndrome (SFTS) is an emerging tick-borne disease caused by Bandavirus dabieense (SFTS virus [SFTSV]). Recently, at least 6 different genotypes of SFTSV have been identified, with genotypes A, D, and F dominant in China and B dominant in Japan and Korea. This study investigated the effect of SFTSV genotypes circulating in South Korea on disease severity, viral load, and cytokine profile.Methods We prospectively enrolled 70 patients with SFTS from July 2015 to June 2022. Serial plasma samples were obtained during hospitalization and analyzed. Viral load was measured by real-time reverse-transcription polymerase chain reaction. Partial sequences of the viral genome were analyzed for genotyping. Plasma concentrations of 17 cytokines were measured by multiplex-bead immunoassay.Results Of 70 samples, 51 could be genotyped. Genotype B was predominant (80.4%) and other genotypes were uncommon. Intensive care unit admission rates (51.2% vs 50.0%) and mortality rates (26.8% vs 40.0%) did not show any significant differences between genotype B and non-B genotypes. The initial viral load did not show any significant differences (3.59 vs 3.64 log copies/mu L), whereas viral load measured at hospital day 3-4 tended to be higher in genotype B than non-B genotypes (3.83 vs 1.83 log copies/mu L, P = .07). Additionally, the plasma concentrations of interferon-alpha, interleukin 10, and interferon-gamma-induced protein 10, which are closely related to mortality in cases of SFTS, did not show any significant differences.Conclusions SFTSV genotype B was the prevalent genotype in South Korea, with no genotype-specific difference in clinical outcomes, initial viral load, or cytokine profiles. We analyzed genotypes of severe fever with thrombocytopenia syndrome (SFTS) virus circulating in South Korea. The majority of analyzed cases was classified as genotype B. There were no genotype-specific differences in factors associated with fatal outcome of SFTS.