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A mutation is a change in the sequence of bases of DNA or RNA in a genome. Some mutations occur during replication of the genome due to errors made by the polymerase enzymes that replicate DNA or RNA. Unlike DNA polymerase, RNA polymerase is prone to errors because it is not capable of “proofreading” its work. Viruses with RNA-based genomes, like HIV, therefore accrue mutations faster than viruses with DNA-based genomes. Because mutation and recombination provide the raw material...
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A single nucleotide polymorphism or SNP is a single nucleotide variation at a specific genomic position in a large population. It is the most prevalent type of sequence variation found in the human genome. Point mutations that occur in more than 1% of the population qualify as SNPs. These are present once every 1000 nucleotides on an average in the human genome. Replacement of a purine with another purine (A/G) or a pyrimidine with another pyrimidine (C/T) is known as a transition. In contrast,...
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Rous Sarcoma virus or RSV was discovered by F. Peyton Rous in the year 1911 as a filterable transmissible agent that could cause tumors in chickens. He won a Nobel Prize for this discovery in 1966. His experiments clearly demonstrated that some cancers could be caused by infectious agents and led to the discovery of many more cancer-causing viruses in animals as well as humans.
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RNA viruses are categorized into positive-strand, negative-strand, or double-stranded groups based on their genomic structure and replication mechanisms. This classification dictates how they exploit host cellular machinery for protein synthesis and replication. Some RNA viruses also utilize reverse transcription as part of their life cycle, further diversifying their replication strategies.Positive-Strand RNA VirusesPositive-strand RNA viruses have genomes that function directly as messenger...
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Origin and evolution of SARS-CoV-2.

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The SARS-CoV-2 virus, causing COVID-19, has spread globally due to its efficient replication and emergent variants. Continued global monitoring is essential for preparedness against future pandemic threats.

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Area of Science:

  • Virology
  • Epidemiology
  • Public Health

Background:

  • Severe acute respiratory syndrome-associated coronavirus 2 (SARS-CoV-2) emerged in 2019, causing the COVID-19 pandemic.
  • Unlike SARS-CoV, SARS-CoV-2 has spread globally in an immunologically naive population.
  • Viral variants, such as Omicron, exhibit immune escape and increased transmissibility, posing ongoing challenges.

Purpose of the Study:

  • To summarize the global spread and evolution of SARS-CoV-2.
  • To highlight the significance of viral variants and immune escape.
  • To emphasize the need for continued global monitoring of SARS-CoV-2 and the animal-human interface.

Main Methods:

  • Review of epidemiological data on SARS-CoV-2 spread.
  • Analysis of viral evolution, including the emergence of variants.
  • Assessment of vaccine impact and immune escape mechanisms.

Main Results:

  • SARS-CoV-2 has spread globally, unlike the contained SARS-CoV outbreak.
  • Emergent variants demonstrate increased infectivity and immune evasion.
  • Vaccines reduce severe disease but do not predict viral extinction.

Conclusions:

  • Global monitoring of SARS-CoV-2 evolution, including variants like Omicron, is critical.
  • Understanding the zoonotic origin and animal-human interface is key to future pandemic preparedness.
  • Continued vigilance and research are necessary to manage the ongoing COVID-19 pandemic.