A large new study, led by a team of geneticists from University College London and published in the peer-reviewed journal Nature Communications, has investigated over 10,000 mutations to the SARS-CoV-2 virus and concluded there currently does not appear to be any variant that is more infectious or transmissible.
Those closely following COVID-19 news cycles are probably familiar with the near-constant parade of headlines that have been published since the beginning of the year proclaiming the virus has mutated and we now have strains that are more infectious, or more deadly. However, as vaccine charity GAVI explains, viruses are mutating all the time, and the vast majority of mutations mean absolutely nothing in regards to how deadly or infectious a virus may be.
“A mutation is simply a change in the virus’ genome: the set of genetic instructions that contain all the information that the virus needs to function,” a statement from GAVI explains. “When the virus replicates, this set of instructions needs to be copied, but errors can creep in during this process. Depending on where in the genome mistakes occur, they can have a negative or positive impact on the virus’ ability to survive and replicate. Or, as is the case the majority of the time, they may have no impact at all.”
SARS-CoV-2 is arguably the most studied virus of all time. Ever since it appeared in late 2019 scientists have been tracking its evolution closely. Lucy van Dorp, from University College London’s Genetics Institute, has been following the virus’s genomic shifts since the beginning.
“The number of SARS-CoV-2 genomes being generated for scientific research is staggering,” says van Dorp. “We realized early on in the pandemic that we needed new approaches to analyze enormous amounts of data in close to real time to flag new mutations in the virus that could affect its transmission or symptom severity.”
In a new study the research team looked at a global dataset of virus genomes from more than 40,000 people spanning 99 countries. The study detected 12,706 unique genomic mutations and eventually homed in on 185 specific mutations that had arisen independently on at least three occasions. Recurrent independent mutations are important because if the same mutations arise frequently it would suggest they are the result of adaptive pressure.
Generating a model of the virus’s evolutionary tree, the researchers then investigated whether any of these specific recurrent mutations showed increasing levels of commonality compared to other closely related virus variants. The researchers could not detect any mutation that appeared to be more infectious or transmissible.
“To date, the fact that none of the 185 recurrent mutations in the SARS-CoV-2 population we identified as candidates for putative adaptation to its novel human host are statistically significantly associated with transmission suggests that the vast majority of mutations segregating at reasonable frequency are largely neutral in the context of transmission and viral fitness,” the researchers conclude in the newly published study.