Effect of genomic variations in severe fever with thrombocytopenia syndrome virus on the disease lethality

A surveillance in a region of China for severe fever with thrombocytopenia syndrome virus (SFTSV) demonstrated that seven clades of viruses are identified and the highest disease lethality is associated with the clade IV. A pronounced inflammation characterized by the expression of CXCL9, IL-10, IL-6, IP-10, M-CSF and IL-1b was observed in the clade IV-infected patient's sera. The enhanced expression of these cytokines was also detected in the clade IV-inoculated PBMC and -mice. The neutralizing activity of convalescent serum from patients infected with a clade was remarkably reduced to other clades, indicating that a cross-clade effect in developing the vaccine is required.