As COVID-19 cases continue to rise in the country, some states and cities seem to be more severely impacted. While multiple reasons could be at play for this, a theory that has come up is that a more ‘virulent’ or deadlier strain of the novel coronavirus may be responsible for the difference in severity.
A PTI report quoted doctors in Indore as saying, “We have a feeling the strain is definitely more virulent in Indore belt. We have discussed this with the NIV and will be sending samples for them to compare by extraction of virus genome.”
But do such variations in the virus’ virulence exist? FIT spoke to two leading virologists who said that there is no basis to show that a particular mutation of the virus is deadlier than the other. Let’s evaluate the evidence.
The Virus Mutates; But All Mutations Are Equally Virulent
Several studies have looked into the genome sequencing of the novel coronavirus and found that it is, indeed, mutating. But for an RNA virus such as this, mutations are normal and are a part of its life cycle due to an error-prone replication process. FIT had earlier reported on these mutations and explained how they could also make the virus less potent.
To put it simply, this is how SARS-CoV-2 (the novel coronavirus) mutates: When an RNA virus comes in touch with a host cell, it starts replicating and possibly changing. Most of these changes are small, and the new virus is not very different in its make-up from the original virus. Flu and measles are both RNA viruses, and prone to changes or mutations.
More recently, scientists at the National Institute of Biomedical Genomics (NIBMG), Kalyani, West Bengal, found that SARS-Cov-2 has undergone mutations to form 10 different types (clades), and among these, the A2a type may be more prominent.
But does evidence for a virus mutating translate into the formation of more ‘dangerous’ types of it?
Dr Jacob T John, a veteran virologist explained, “The novel coronavirus is a single-stranded RNA virus. Mutating is the rule for such viruses, not the exception. Right now, these don’t mean anything in terms of the virus’ lethality or virulence. There is just a slight variation, but the major behaviour, properties, themes, characteristics and the virulence, are all still the same.”
"Even the paper from NIBGM mentions in the end that these findings may or may not be indicative of a problem. They are merely describing a phenomenon, not linking it to a particular outcome. It’s a well-done study, but we don’t need to bother about the implications of the results,” he added.
Dr Shahid Jameel, a Virologist and CEO of Wellcome Trust DBT India Alliance, said the same thing. “Viruses are constantly changing in their sequence and there are thousands of sequences available for the novel coronavirus. The mutations may be more frequent at certain positions in the genome. People start naming the groups (also called clades) based on these changes. We don’t need to be bogged down by the various terms, they simply represent the dominant changes in the viral chain. There is no basis for saying that the mutations behave differently from each other in terms of their severity.”
Speaking about the virulence and transmissibility, he said,
Soumya Swaminathan, Chief Scientist at the World Health Organization, told The Print in an online conversation, “Some clades are more prevalent in certain geographical regions than in others. But none of these seems to have any differences in clinical outcome, mortality, virulence, or transmissibility.”
There may be a possibility that some clades are circulating faster, but there isn’t much clarity about that either, says Dr Jameel. “Once we understand the outbreak a little better, once we map more sequences and their trajectories, we may know otherwise. But for now, there is no evidence that they have any implication. We don’t even think these mutations will infringe too much upon vaccine development because the parts of the virus that are critical in that process, are undergoing only insignificant changes, and most viruses retain their basic make-up.”
An article published in the journal Nature, titled ‘We Shouldn’t Worry When a Virus Mutates During Disease Outbreaks’, summarized the point well, “Mutations are not indicative of outlandish and devastating new viral characteristics. Instead, they can inform our understanding of emerging outbreaks. Any claims over the consequences of mutation demand careful experimental and epidemiological evidence.”
“Therefore, claiming that a more virulent strain is responsible for more cases in certain states and cities is completely baseless,” Dr Jameel says.