With the emergence of a new, more infectious mutation of Covid-19 across southern England including London, a growing number of countries are barring travel from the UK. This comes after British Prime Minister Boris Johnson announced that the new variant is 70 percent more transmissible than existing strains. But what is mutation and why do viruses mutate?
Mutation isn’t specific to Covid-19. It’s a common feature of viruses and bacteria. “Viruses mutate all the time and they do it in different ways,” says Dr Camille Locht of the Institut Pasteur de Lille.
"One classic example is that of the AIDS virus that mutates so fast that no vaccine works against it,” he says. The influenza virus also mutates frequently which is why we need a vaccine every year to protect against its new strain.
According to Dr Locht, every organism that has a genetic code, whether DNA or RNA, mutates. The mutation is more frequent in RNA viruses such as those responsible for Covid-19, AIDS and Influenza.
“When a DNA-based organism makes a copy of itself, its highly effective repair system corrects errors in the genetic code. It turns out that for RNA, the repair system isn’t that effective, resulting in more variants,” he says.
There is no design behind these mutations. Rather, they occur randomly and for most of the time, the mutations are neutral or even disadvantageous for the organisms. “It’s rare that a mutation works to their advantage, like we see with the HIV and now we are seeing with Covid-19,” Locht says.
In viruses such as Coivd-19, the RNA is the genetic material that codes for all the proteins responsible for different functions. For example, the spike protein in Sars-CoV-2 helps it to bind to the cell receptors.
From what is known so far, the reason behind Sars-CoV-2's new strain becoming more infectious is due to the mutations in the genes of its spike protein.
“The mutation in spike protein makes it easier to bind to receptors of human cells. Of course, this still has to be confirmed with more rigorous analyses.
"But if that happens to be the case, the virus might become more infectious and be able to integrate into the host much quicker than the old variant. This, therefore, makes it spread faster.”
However, Dr Locht stresses that though these mutations could mean that the virus has become more fit to infect, it doesn’t necessarily indicate that it has become more dangerous or deadlier.
It has already undergone a number of mutations. “This virus is known to have jumped from animals to humans. There are viruses that go from animals to humans but they don’t spread from human to human. But sometimes they undergo mutations that result in their human-to-human spread. This is what happened with Covid-19.”
“If you compare the genome of the virus that was isolated from bats to the genome of the virus of the first Covid-19 patient, there are a huge number of changes between the two variants,” he says.
While understandably there’s a fear now with the new variant of Sars-CoV-2, the process of mutation is integral to every DNA and RNA based organism. “Mutation is something that cannot be controlled. In fact, this is what drives evolution. Without it, evolution won’t be possible and we wouldn’t exist,” Dr Locht says.