SFTS virus is a tick-borne virus in the genus '' Bandavirus'' in the family '' Phenuiviridae''. 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 2009 and now has also been discovered in Japan, South Korea, Vietnam and Taiwan in 2015. SFTS has a fatality rate of 12% and as high as over 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. Another outbreak occurred in East China in the early half of 2020.

History

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

Genome

The sequence of the genome was published in 2011. There are three segments—large (L), medium (M) and small (S). Five proteins have been identified—an RNA dependent RNA polymerase (RdRp), 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 In molecular biology, reading frames are defined as spans of DNA sequence between the start and stop codons. Usually, this is considered within a studied region of a prokaryotic DNA sequence, where only one of the six possible reading frames ...

encoding 1073 amino acid precursors of glycoproteins (Gn and Gc). The S segment has 1746 nucleotides of ambisense RNA encoding two proteins, the N and NSs proteins. These lie in opposite orientations and are separated by a 54 nucleotide intergenic region.

Evolution

The virus originated 50–150 years ago and has undergone a recent population expansion. Five genotypes (A–E) have been identified. Strains from

China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...

could be grouped into all five genotypes while isolates from

South Korea South Korea, officially the Republic of Korea (ROK), is a country in East Asia. It constitutes the southern half of the Korea, Korean Peninsula and borders North Korea along the Korean Demilitarized Zone, with the Yellow Sea to the west and t ...

lay in three (types A, D and E) and those from

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

only in one (type E). The virus appears to have originated in the

Dabie Mountains The Dabie Mountains () are a major mountain range located in central China. Running northwest-to-southeast, they form the main watershed between the Huai River, Huai and Yangtze rivers. The range also marks the boundary between Hubei Province (n ...

in central China between 1918 and 1995. Among bunyaviruses, 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.

Life cycle

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

cat The cat (''Felis catus''), also referred to as the domestic cat or house cat, is a small domesticated carnivorous mammal. It is the only domesticated species of the family Felidae. Advances in archaeology and genetics have shown that the ...

mice A mouse (: mice) is a small rodent. Characteristically, mice are known to have a pointed snout, small rounded ears, a body-length scaly tail, and a high breeding rate. The best known mouse species is the common house mouse (''Mus musculus' ...

hedgehog A hedgehog is a spiny mammal of the subfamily Erinaceinae, in the eulipotyphlan family Erinaceidae. There are 17 species of hedgehog in five genera found throughout parts of Europe, Asia, and Africa, and in New Zealand by introduction. The ...

weasel Weasels are mammals of the genus ''Mustela'' of the family Mustelidae. The genus ''Mustela'' includes the least weasels, polecats, stoats, ferrets, and European mink. Members of this genus are small, active predators, with long and slend ...

brushtail possum The brushtail possums are the members of the genus ''Trichosurus'' in the Phalangeridae, a family of marsupials. They are native to Australia (including Tasmania) and some small nearby islands. Unique among marsupials, they have shifted the hyp ...

s 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 Ticks are parasitic arachnids of the order Ixodida. They are part of the mite superorder Parasitiformes. Adult ticks are approximately 3 to 5 mm in length depending on age, sex, and species, but can become larger when engorged. Ticks a ...

, '' 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.

Epidemiology

This virus has been found in the Chinese provinces of

Anhui Anhui is an inland Provinces of China, province located in East China. Its provincial capital and largest city is Hefei. The province is located across the basins of the Yangtze and Huai rivers, bordering Jiangsu and Zhejiang to the east, Jiang ...

Henan Henan; alternatively Honan is a province in Central China. Henan is home to many heritage sites, including Yinxu, the ruins of the final capital of the Shang dynasty () and the Shaolin Temple. Four of the historical capitals of China, Lu ...

Hubei Hubei is a province of China, province in Central China. It has the List of Chinese provincial-level divisions by GDP, seventh-largest economy among Chinese provinces, the second-largest within Central China, and the third-largest among inland ...

Jiangsu Jiangsu is a coastal Provinces of the People's Republic of China, province in East China. It is one of the leading provinces in finance, education, technology, and tourism, with its capital in Nanjing. Jiangsu is the List of Chinese administra ...

Liaoning ) , image_skyline = , image_alt = , image_caption = Clockwise: Mukden Palace in Shenyang, Xinghai Square in Dalian, Dalian coast, Yalu River at Dandong , image_map = Liaoning in China (+all claims hatched).svg , ...

and

Shandong Shandong is a coastal Provinces of China, province in East China. Shandong has played a major role in Chinese history since the beginning of Chinese civilization along the lower reaches of the Yellow River. It has served as a pivotal cultural ...

. 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, Japan, Vietnam and Taiwan.

References

{{Taxonbar, from=Q5313087, from2=Q24809104, from3=Q57756649 Arthropod-borne viral fevers and viral haemorrhagic fevers Hematology Insect-borne diseases Phleboviruses Zoonotic viral diseases