Group V ((−)ssRNA)
The SFTS virus is a tick-borne phlebovirus in the order Bunyavirales. It appears to be more closely related to the Uukuniemi virus serogroup than to the Sandfly fever group. It is a member of the Bhanja virus serocomplex.
The clinical condition it caused is known as severe fever with thrombocytopenia syndrome (SFTS). SFTS is an emerging infectious disease that was first described in northeast and central China and now has also been discovered in Japan and South Korea. SFTS has a fatality rate of 12% and as high as 30% in some areas. The major clinical symptoms of SFTS are fever, vomiting, diarrhea, multiple organ failure, thrombocytopenia (low platelet count), leukopenia (low white blood cell count) and elevated liver enzyme levels.
In 2009 Xue-jie Yu and colleagues isolated the SFTS virus (SFTSV) from SFTS patients’ blood.
The genome has been sequenced. There are three segments—large (L), medium (M) and small (S). Six proteins have been identified—an RNA dependent RNA polymerase (RdRp), a glycoprotein precursor (M), a glycoprotein N (Gn), a glycoprotein C (Gc), a nuclear protein (NP) and a non structural protein (NSs).
The L segment encodes the RNA polymerase with 2084 amino acid residues.
The M segment encodes one open reading frame encoding 1073 amino acid precursors of glycoproteins (Gn and Gc).
The S segment has 1744 nucleotides of ambisense RNA encoding two proteins, the N and NSs proteins. These lie in opposite orientations and are separated by a 62 nucleotide intergenic region.
Five genotypes (A–E) have been identified. Strains from China could be grouped into all five genotypes while isolates from South Korea lay in three (types A, D and E) and those from Japan only in one (type E). The virus appears to have originated in the Dabie Mountains in central China between 1918 and 1995.
SFTSV is a tick-borne virus; it is not clear whether it can be transmitted by other blood-sucking arthropods. It can infect many mammalian hosts, including cats, mice, hedgehogs, weasels, brushtail possums and yaks. Humans appear to be accidental hosts, and play no essential role in the life cycle of SFTSV. SFTSV has been detected from the ixodid tick, Haemaphysalis longicornis, Ixodes nipponensis, Amblyomma testudinarium and Rhipicephalus microplus. In addition to tick bite, SFTSV can be transmitted from person to person through contact with blood or mucus of an infected person.
This virus has been found in the Chinese provinces of Anhui, Henan, Hubei, Jiangsu, Liaoning and Shandong. SFTS occurs in rural areas, from March to November, and a majority of cases are found from April to July.
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