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New Covid-19 variants in US - More contagious?
Read more on - Polity | Economy | Schemes | S&T | Environment
- SARS-COV-2 Virus: Researchers are tracking virus variants since some of them might be more deadly than the original virus, they may be more easily transmissible and can have repercussions on the effectiveness of vaccines. Researchers have reported seven new variants of the SARS-CoV-2 virus in the US. They are tracking virus variants since some of them might be more deadly than the original virus, they may be more easily transmissible and can have repercussions on the effectiveness of vaccines.
- Known variants of SARS-CoV-2:
- B.1.1.7: This variant emerged in the UK and may be associated with an increased risk of death compared with other variants, the US Centers for Disease Control and Prevention (CDC) has said.
- B.1.351: This variant emerged independently from the UK variant and was first identified in South Africa. It was also reported in the US by the end of January 2021.
- P.1: This variant emerged in Brazil and is known to have 17 unique mutations. Three of them are in the receptor-binding domain of the spike protein (the spike protein, which protrudes from the surface of the virus is one of the key reasons that SARS-CoV-2 has been able to spread so rapidly and therefore, any mutations that affect the spike protein are important to understand).
- Learnings: Authors of a recent study say that in areas where the prevalence of the virus is high, selection pressures might have favoured the emergence of variants that evade neutralising antibodies (the proteins that prevent the virus from infecting once it is inside the body). The seven new lineages noted by the researchers have all evolved a mutation in the same genetic letter, which affects the way the virus enters the human cells. But it is not yet clear if this mutation makes these new variants more contagious and more dangerous.
- Why do viruses mutate: Evolution helps organisms to change in response to certain changes in the environment. The goal here is to help the organism adapt so it can survive. In the Naked Ape trilogy, zoologist Desmond Morris writes about how humans have adapted to their changing environment over the course of millions of years of evolution. Since viruses can only replicate within a host cell, their evolution is influenced by their hosts. This means that the virus will mutate in order to evade the defenses that its hosts put up for it.
- DNA versus RNA: As compared to DNA viruses, RNA viruses (SARS-CoV-2 is an RNA virus) have much higher mutation rates, probably one mutation per genome copy. Mutations might be deleterious, neutral and occasionally, they may be favourable. The book notes that only those mutations that do not interfere with the essential virus functions can persist in a given population. Compared to the HIV virus that causes AIDS, the SARS-CoV-2 virus is changing much more slowly as it spreads. But like humans influence the evolution in viruses, viruses too, have shaped the way humans have evolved. About 30 per cent of all protein (proteins help cells to perform their functions) adaptations in humans since their divergence from chimpanzees have been driven by viruses.
- What is a mutation: Once a virus has entered the body of its host, in order to infect the host it starts replicating, which means making copies of its entire genetic sequence. But every once in a while, the virus makes mistakes during replication. These mistakes, typically a change in a single letter (each coronavirus has about 30,000 RNA letters) among the thousands in the virus’s sequence, might change the properties of the virus’s proteins and therefore, change its capabilities. This is a mutation and if it is a favourable mutation, it can give the virus a new ability that promotes its reproduction, which helps the virus to become more widespread over generations.
- Mutations and vaccines: Resources should be spent on developing ‘pan-virus vaccines’ that can provide immunisation against multiple strains of a virus. This is necessary in the context of SARS-CoV-2, since it is already evolving and initial evidence shows that some of its strains are more easily transmissible. Vaccine development for the first four human coronaviruses, which include HCoV-229E (one of the first strains to be described in the mid-1960s), HCoV-OC43 (discovered between mid-late 1960s), HCoV-NL63 and HCoV-HKU1 (NL63 and HKU1 both discovered in Hong Kong in early 2005) was not a priority since these cause only mild illness. It was only two decades ago when SARS-CoV was emerging in China around 2003 that the need to develop a vaccine was felt since it was the first example of a human coronavirus that could cause serious illness.
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