Clinical Characteristics and Immune Status of Patients with Severe Fever with Thrombocytopenia Syndrome.

Severe fever with thrombocytopenia syndrome (SFTS) is a novel infectious disease caused by bunya virus. The purpose of this study was to investigate the clinical characteristics of SFTS patients and their virus-related immune disorders . Patients with SFTS admitted to Nanjing Drum Tower Hospital from 2017 to 2020 were retrospectively analyzed, and divided into survival group and death group according to the 28-day survival. Clinical characteristics and laboratory examination results of SFTS patients were recorded, and dynamic changes of immune function and inflammatory factors were statistically analyzed. Prolonged activated prothrombin time (APTT) ( = 0.001), high viral load ( = 0.001), and elevated human leukocyte antigen DR (HLA-DR) level ( = 0.002) were independent prognostic risk factors for SFTS patients. Compared to the survival group, the nonsurvival group was more prone to hemorrhagic and neurological symptoms ( < 0.05). Natural kill (NK) cell count, interleukin-10, interferon-, and tumor necrosis factor- scores in the nonsurvival group continued to increase after admission, while CD3 T, CD4 T, and CD8 T cell counts continued to decrease. CD3 T lymphocyte count was negatively correlated with viral load ( = 0.3883,  < 0.001), CD4 T lymphocyte count was negatively correlated with viral load ( = 0.28933,  < 0.001), CD8 T lymphocyte count was negatively correlated with viral load ( = 0.781,  < 0.001), and HLA-DR was positively correlated with viral load ( = 0.489,  < 0.001). High viral load, prolonged APTT time, and elevated HLA-DR level are independent prognostic risk factors for SFTS patients. The T lymphocyte subsets of SFTS patients continue to decrease after infection, and the number of T lymphocyte subsets can reflect the severity of the disease.