There is no evidence that mutations in the coronavirus facilitate the spread of the virus, researchers said.
Professor François Balloux, co-author of the research at University College London, said the results were a surprise, but rare good news.
"I have to admit that I expected the virus to progress to even higher transmission," he told the Guardian. "This is really good news that is not happening and it is unlikely to happen in the near future."
Balloux said he understood why there were concerns about the deployments. But, he said, "Basically, the mutations, especially here, are not to be feared. It's just some sort of minor typo [in the genome] which are either neutral or often not very favorable to the virus. "
The study, which has not yet been peer reviewed, has been performed by a team of researchers in the UK and France, which has examined more than 15,000 coronavirus genomes collected from patients worldwide since the start of the epidemic.
In all genomes, they discovered 6,822 mutations in total, compared to the ancestral genome, but none of the genomes showed more than 29 unique position changes.
Further analysis revealed that 273 of the mutations recurred multiple times – the team focusing on the 31 mutations that appear to have occurred independently at least 10 times.
"There is no European, American, Icelandic variety – there has been a lot of mixing since the start of the pandemic," said Balloux.
"If there is a mutation that appears and makes it transmit better, then we should see it happen several times," he added. "If you have a mutation that happened once during the pandemic, then it is very unlikely that anything beneficial [to the virus]. "
They then examined whether these mutations made the virus more transmissible. "We are just trying to find out if those who carry a mutation, if they have more descendants, if they spread faster [than closely related genomes without the mutation] – and the answer is no, "said Balloux, adding that the mutations could be introduced by enzymes involved in the body's immune system. In fact, according to the team, some of the mutations studied seem to be actually harmful to the virus.
Balloux added that although there is not yet enough data to explore whether the mutations can make the virus more deadly or cause more severe symptoms, he said it was unlikely .
“Viruses do not benefit from killing their hosts. There is no evolutionary benefit to them from hurting their hosts, "he said. "We really do not expect the virus to become more virulent."
Martin Hibberd, professor of emerging infectious diseases at the London School of Hygiene and Tropical Medicine who was not involved in the study, praised the results.
But, he added, the relatively small sample size and the fact that samples tend to be collected in more severe cases of Covid-19 means that more research is needed to explore how genetic variations can affect the transmission or virulence of the virus.
Among other considerations, Hibberd said: "Additional monitoring is also necessary as circumstances change – such as changing locking conditions – which could change the transmission environment."