Clinical Aspects of SFTS

Abstract

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging tick-born disease. The incubation period after tick-bite is generally 6–14 days. The typical course of SFTS has three clinical stages, the “fever stage”, the “multiple organ failure stage”, and the “convalescent stage”. The clinical symptoms include sudden onset of high fever, chills, headache, myalgia, gastrointestinal symptoms, lymphadenopathy, hemorrhagic tendency, and central nervous system (CNS) manifestations. SFTS frequently accompanies with hemophagocytic lymphohistiocytosis. Common laboratory findings include leukocytopenia, thrombocytopenia, elevated levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactic acid dehydrogenase (LDH), and creatine kinase (CK). Blood coagulation times are prolonged. Notably, the level of C-reactive protein remains normal range. The levels of inflammatory cytokines are associated with clinical severity of SFTS. Diagnosis of SFTS is confirmed by reverse transcriptase polymerase chain reaction for SFTS virus genome. SFTS should be differentially diagnosed with human granulocytic anaplasmosis, hemorrhagic fever with renal syndrome, spotted fever group rickettsioses, dengue fever, and leptospirosis. Prognostic risk factors of SFTS include older age, high SFTS virus load, CNS manifestations, elevated levels of AST, ALT, LDH, and CK, abnormal values of coagulation factors, disseminated intravascular coagulation, renal failure, elevated levels of inflammatory cytokines, and delay in making diagnosis.