Severe Fever with Thrombocytopenia Syndrome (SFTS) is an emerging infectious disease caused by a novel bunyavirus. Until recently, SFTSV-associated encephalitis remained largely uninvestigated.

We made clinical investigation on SFTS patients who experienced encephalitis in one reference hospital in Henan Province from 2011 to 2013 to identify the risk factors for encephalitis occurrence and their fatal outcome development.

Altogether 538 SFTS patients were included and 19.1% of them developed encephalitis. Fatal outcome occurred in 44.7% of the encephalitis patients. The risk factors associated with encephalitis occurrence and death included older age, longer delay between disease onset and hospital admission, pre-existing diabetes and myalgias, as well as the laboratory evaluations of higher virus load on admission, decreased WBC, PLT count, lymphocyte percentage and ALB, elevated neutrophils percentage, AST, ALT, LDH, CK, ALP, GGT, BUN and CREA. These parameters could be used as potential predictors referring to severe SFTS cases. One SFTSV strain was isolated from cerebrospinal fluid sample. Cytokine/chemokine assay revealed that blood EOTAXIN, IFN-γ, IL-15, IL-6, IP-10, TNF-α were remarkably elevated before clinical deterioration in the confirmed encephalitis patient.

SFTSV is capable of infecting the central nervous system and screening for SFTSV in encephalitis of unknown reason should be performed in SFTS endemic regions. The encephalitis occurrence and fatal outcome could be potentially predicted by clinical and laboratory evaluations.