SFTS virus

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Phleboviruses
Virus classification
Group: Group V ((−)ssRNA)
Order: Bunyavirales
Family: Phenuiviridae
Genus: Phlebovirus
Species: SFTS virus

The SFTS virus is a tick-borne phlebovirus in the order Bunyavirales.[1] It appears to be more closely related to the Uukuniemi virus serogroup than to the Sandfly fever group.[1] It is a member of the Bhanja virus serocomplex.[2]

The clinical condition it caused is known as severe fever with thrombocytopenia syndrome (SFTS).[1] 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.

History[edit]

In 2009 Xue-jie Yu and colleagues isolated the SFTS virus (SFTSV) from SFTS patients’ blood.[1]

Genome[edit]

The genome has been sequenced.[1] 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.

Evolution[edit]

Five genotypes (A–E) have been identified.[3] 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.

Life cycle[edit]

SFTSV is a tick borne virus, it is not clear whether it can be transmitted by other blood sucking arthropods.[4] 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[5] and Rhipicephalus microplus.[6] In addition to tick bite, SFTSV can be transmitted from person to person through contact with blood or mucus of an infected person. [7][8]

Epidemiology[edit]

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.

The virus has also been found in South Korea and Japan.[9][10]

References[edit]

  1. ^ a b c d e Fever with thrombocytopenia associated with a novel Bunyavirus in China. N Engl J Med. 2011 Mar 16. Full text
  2. ^ Matsuno, K. "Characterization of the Bhanja serogroup viruses (Bunyaviridae): a novel species of the genus Phlebovirus and its relationship with other emerging tick-borne phleboviruses". J Virol. 87: 3719–28. doi:10.1128/JVI.02845-12. PMC 3624231Freely accessible. PMID 23325688. 
  3. ^ Liu JW, Zhao L, Luo LM, Liu MM, Sun Y, Su X, Yu XJ (2016). "Molecular evolution and spatial transmission of severe fever with Thrombocytopenia Syndrome Virus based on complete genome sequences". PLOS ONE. 11 (3): e0151677. doi:10.1371/journal.pone.0151677. PMC 4801363Freely accessible. PMID 26999664. 
  4. ^ Luo, LM. "Haemaphysalis longicornis Ticks as Reservoir and Vector of Severe Fever with Thrombocytopenia Syndrome Virus in China". Emerging Infectious Diseases. 21: 1770–6. doi:10.3201/eid2110.150126. PMC 4593435Freely accessible. PMID 26402039. 
  5. ^ "Detection of SFTS Virus in Ixodes nipponensis and Amblyomma testudinarium (Ixodida: Ixodidae) Collected From Reptiles in the Republic of Korea". J Med Entomol. Retrieved 5 February 2017. 
  6. ^ Zhang YZ; et al. (2012). "The Ecology, Genetic Diversity, and Phylogeny of Huaiyangshan Virus in China". J. Virol. 86 (4): 2864–68. doi:10.1128/JVI.06192-11. PMC 3302241Freely accessible. PMID 22190717. 
  7. ^ Liu, Y. "Person-to-person transmission of severe fever with thrombocytopenia syndrome virus". Vector Borne Zoonotic Dis. 12 (2): 156–60. doi:10.1089/vbz.2011.0758. PMID 21955213. 
  8. ^ Bao, CH. "A family cluster of infections by a newly recognized bunyavirus in eastern China, 2007: further evidence of person-to-person transmission". Clin Infect Dis. 53: 1208–1214. doi:10.1093/cid/cir732. 
  9. ^ Kim, KH. "Severe Fever with Thrombocytopenia Syndrome, South Korea, 2012". Emerg Infect Dis. 19: 1892–4. doi:10.3201/eid1911.130792. PMC 3837670Freely accessible. PMID 24206586. 
  10. ^ Takahashi, T. "The First Identification and Retrospective Study of Severe Fever With Thrombocytopenia Syndrome in Japan". J Infect Dis. 209: 816–827. doi:10.1093/infdis/jit603.