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What causes flavivirus disease?
Species of Flaviviridae are transmitted by either insects or arachnids and cause severe diseases such as yellow fever, dengue, tick-borne encephalitis, and Japanese B encephalitis.
What is flavivirus infection?
Flaviviruses are group of single stranded RNA viruses that cause severe endemic infection and epidemics on a global scale. It presents a significant health impact worldwide and the viruses have the potential to emerge and outbreak in a non-endemic geographical region.
What is the mode of transmission for flavivirus?
Yellow fever virus is an RNA virus that belongs to the genus Flavivirus. It is related to West Nile, St. Louis encephalitis, and Japanese encephalitis viruses. Yellow fever virus is transmitted to people primarily through the bite of infected Aedes or Haemagogus species mosquitoes.
How can Flavivirus be prevented?
Flaviviral infection can be prevented by avoiding exposure to the arthropods that transmit these viruses. Personal protective strategies include wearing repellent, staying in screened or air-conditioned dwellings, and avoiding outdoor activities during times when the vectors are most avidly seeking blood meals.
Which mosquito causes dengue virus?
Dengue viruses are spread to people through the bite of an infected Aedes species (Ae. aegypti or Ae. albopictus) mosquito. Almost half of the world's population, about 4 billion people, live in areas with a risk of dengue.
How does Flavivirus cause dengue?
The transmission cycle starts with an adult female Aedes feeding on a dengue infected person. The virus then develops within the mosquito in approximately seven days (shorter in warm weather, longer in cooler weather). Once the mosquito has become infective, it transmits the virus when biting a subsequent human.
Which disease is caused by alphavirus?
Alphaviruses, such as Chikungunya virus, O'Nyong–Nyong virus, Ross River virus, have been widely known to cause fever, rash, and rheumatic diseases.
Why dengue is a Flavivirus?
Dengue virus (DENV) belongs to the family Flaviviridae, genus Flavivirus. It is a single-stranded positive-sense ribonucleic acid virus with 10,700 bases. The genus Flavivirus includes other arthropod borne viruses such as yellow fever virus, West Nile virus, Zika virus, tick-borne encephalitis virus.
Overview
Flavivirus is a genus of positive-strand RNA viruses in the family Flaviviridae. The genus includes the West Nile virus, dengue virus, tick-borne encephalitis virus, yellow fever virus, Zika virus and several other viruses which may cause encephalitis, as well as insect-specific flaviviruses (ISFs) such as cell fusing agent virus (CFAV), Palm Creek virus (PCV), and Parramatta River virus (PaRV). …
Structure
Flaviviruses are enveloped and spherical and have icosahedral geometries with a pseudo T=3 symmetry. The virus particle diameter is around 50 nm.
Genome
Flaviviruses have positive-sense, single-stranded RNA genomes which are non-segmented and around 10–11 kbp in length. In general, the genome encodes three structural proteins (Capsid, prM, and Envelope) and seven non-structural proteins (NS1, NS2A, NS2B, NS3, NS4A, NS4B, NS5). The genomic RNA is modified at the 5′ end of positive-strand genomic RNA with a cap-1 structure (me -GpppA-me ).
Life cycle
Flaviviruses replicate in the cytoplasm of the host cells. The genome mimics the cellular mRNA molecule in all aspects except for the absence of the poly-adenylated (poly-A) tail. This feature allows the virus to exploit cellular apparatuses to synthesize both structural and non-structural proteins, during replication. The cellular ribosome is crucial to the replication of the flavivirus, a…
RNA secondary structure elements
The positive sense RNA genome of Flavivirus contains 5' and 3' untranslated regions (UTRs).
The 5'UTRs are 95–101 nucleotides long in Dengue virus. There are two conserved structural elements in the Flavivirus 5'UTR, a large stem loop (SLA) and a short stem loop (SLB). SLA folds into a Y-shaped structure with a side st…
The role of RNA secondary structures in sfRNA production
Subgenomic flavivirus RNA (sfRNA) is an extension of the 3' UTR and has been demonstrated to play a role in flavivirus replication and pathogenesis. sfRNA is produced by incomplete degradation of genomic viral RNA by the host cells 5'-3' exoribonuclease 1 (XRN1). As the XRN1 degrades viral RNA, it stalls at stemloops formed by the secondary structure of the 5' and 3' UTR. This pause …
Evolution
The flaviviruses can be divided into two clades: one with the vector-borne viruses and the other with no known vector. The vector clade in turn can be subdivided into a mosquito-borne clade and a tick-borne clade. These groups can be divided again.
The mosquito group can be divided into two branches: one branch contains th…
Taxonomy
In the genus Flavivirus there are 53 defined species:
• Apoi virus
• Aroa virus
• Bagaza virus
• Banzi virus