The more a virus spreads, the faster it mutates and the deadlier are the generated mutants.
Coronaviruses have inhabited this world for quite some time now. The zoonotic nature of the virus allowed them to inhabit the human respiratory system and cause an unwarranted pandemic since February 2020. The spread can be reduced by limiting excessive physical contact, washing hands from time to time and wearing masks. Being an RNA virus, SARS-CoV-2 underwent quite a number of mutations in order to sustain itself. Some of these mutations can be detrimental to the virus itself, some of them do not bring about a change, and some of them can increase virulence. Thus emerged, newer variants that were capable of causing infections with more vigour than their predecessors.
Many of the SARS-CoV-2 mutants are area-specific and most of the developed vaccines are able to protect against more than just one strain. Some of the identified strains are as follows:
- B.1.1.7 lineage: Also known as VOC 202012/01 or 20B/501Y.V1 by the CDC, this variant was first detected in the UK around September 2020. This variant has since been detected in 90 countries across the world and it is said to be 30-50% more infectious and transmissible than the original strains. The SARS-CoV-2 virus interacts with the ACE-2 (angiotensin converting enzyme-2) in the host cell through the spike proteins which contain the receptor binding domain (RBD). The B.1.1.7 variant has a mutation in this particular domain where an asparagine residue is replaced by a tyrosine residue at the 501st (N501Y) position of the protein. There could also be a deletion of an amino acid residue at the 69th and 70th position. Both of these mutations can change the conformation of the spike protein, which can aid in tighter binding of the virus to the host cell and cause the infection.
- B.1.617 lineage: This variant is rapidly spreading all across India. Termed as the “double mutant” strain because of having two crucial mutations namely E484Q (a glutamic acid residue is replaced by a glutamine at the 484th position) and L452R (a leucine residue is replaced by an arginine at the 452nd position). These mutations also affect the structure of the spike protein and prevent it from being neutralised by the antibodies by weakening the interactions between them. Thereby allowing immune escape and increased infectivity.
- B.1.351 lineage: or 20C/501Y.V2 was first observed in South Africa in October 2020 and has hence been seen in 48 countries across the world. This variant also has an N501Y mutation and an E484K (a glutamic acid residue is replaced by a lysine residue) or the ‘Eek’ mutation, both of which change the conformation of the Spike Protein. The B.1.351 variant is not as deadly as the B.1.1.7 variant however it is more transmissible than its parent strains. This variant is concerning to many scientists as many of the vaccines offer less protection against it.
- P.1 lineage: The first incidence of this variant was detected in four people who came back to Japan after a trip to Brazil around January 2021. The roots of this more transmissible variant were traced back to Manaus, Brazil. Being a branch of the larger B.1.1.28 lineage (which is also said to have the Eek mutation), the P.1 variant is the most predominant form found across the South American continent. These viruses have twelve mutations in the spike protein which allows in escaping the rigorous immune screening.
- The CAL.20C variant of the B.1.427 and B.1.429 lineage is most commonly found in California was first detected around December of 2020 and is said to be 20% more infectious than its predecessors. This variant has the L452R mutation as well. Studies suggest that this strain could be more contagious than its earlier forms and has hence been detected in Australia, Europe and parts of Asia
- B.1.618 variant: Also known as the ‘triple mutant’ was detected in West Bengal, India as of April 2021. Scientists state that this variant arose from the double mutant B.1.617 and could be more infective. This variant also carries the Eek mutation allowing it to evade the immunity developed by a previous COVID infection.
The second wave of the COVID-19 pandemic has brought in deadlier and virulent forms. Genome sequencing can help in finding stable regions which can be the target for developing vaccines and drugs.