The scientific community looked on with awe as cases of reinfection of SARS-CoV-2 started trickling in by late August.
Reinfections, on the face of it, need not necessarily mean that the virus has mutated in ways that make it more dangerous, according to researchers. In fact, cases of reinfection are not unusual with viruses.
Viruses mutate all the time and most of these genetic changes are detrimental to the organism. Some studies show that only a tiny minority of these changes could turn out to be beneficial.
Mutability tends to be especially high with RNA viruses. It is through these mutations that viruses evolve. The evolution of SARS-CoV-2, however, is found to be rather slow compared to others of its ilk. Nevertheless, SARS-CoV-2 has already splintered into different variants. These variants
are still very similar, and unlike strains where the virus differs in major biological ways. A viral strain is usually an isolate with a different biological property. It may, for example, bind to a different receptor, or have a distinctly different stability at higher temperatures.
Even as researchers maintain that the virus has not become virulent enough to outgrow a potential vaccine, there is currently little evidence to suggest that these mutations have made it any less harmful than when it first emerged.
More infective D614G
In the course of mutation and development, SARS-CoV-2 acquired a very significant mutation in its spike protein. Named D614G, it represents a change at position 614 of the spike protein — from an aspartic acid (D) to a glycine amino acid (G). The mutation, which probably originated in China, appeared to become more and more frequent with the outbreak in northern Italy in February. Spreading all over the world, this variant of the SARS-CoV-2 has become the dominant one today. COVID-19 Genomics UK Consortium, which analysed 25,000 whole genome SARS-CoV-2 sequences collected in the UK, found the mutation had not increased mortality in patients.
But studies do suggest that D614G mutation does seem to have increased the infectivity of the virus.
Researchers say that while the D614G mutation increases the virus’s infectivity in humans, it is unlikely to have any major implications for the prospects of developing an effective vaccine. The mutation does affect the spike protein, but not the part of it that the neutralising antibodies of the human immune system target when the body defends itself against infection.
6 strains of SARS-CoV-2?
Currently, there are six strains of SARS-COV-2, say researchers at the University of Bologna after analysing 48,635 coronavirus genomes isolated in labs all over the world.
The original SARS-CoV-2 is the L strain that first appeared in Wuhan in December 2019. Its first mutation — the S strain — appeared at the beginning of 2020. Somewhere around mid-January 2020, the V and G strains emerged. As of now, strain G is the most widespread: It has mutated into strains GR and GH at the end of February 2020.
“Strain G and its related strains GR and GH are by far the most widespread, representing 74% of all gene sequences we analysed,” said the study that was published in Frontiers in Microbiology.
But it adds that currently there is no evidence to suggest that the virus has become more virulent or more infectious than it was when it was first detected in Wuhan, Central China, in December.