The lower the number of cases before lockdown restrictions are eased, the less likely it is for new coronavirus mutations to emerge, experts have said.

Every time the virus infects someone it has the opportunity to mutate, and therefore the fewer cases of infection, the less chance it will have to change, scientists say.

It comes as the more transmissible variant, first detected in Kent, is now thought to be the dominant strain in the UK, and as researchers detected a mutation from the South African and Brazilian variant present in some UK cases.

Experts are also concerned new variants that emerge may be more resistant to vaccines.

On Monday, Health Secretary Matt Hancock said the fewer new cases of coronavirus there are, the lower the chance of a new variant appearing domestically.

The more the virus does spread, the more it replicates, the more chances it has to change

Lawrence Young, professor of molecular oncology at Warwick Medical School, told the PA news agency: “The more the virus is allowed to spread, the more people who are infected, the more likely it is that this virus will change and evolve and form new variants.

“Variants have been generated in everybody who’s infected, really, at one level or another.

“The more the virus does spread, the more it replicates, the more chances it has to change.”

He added: “One way of trying to put the can on the lid on the number of variants being generated is to try and control the spread of the virus.”

Prof Young said: “The idea here is if you have a very strong immune response to the virus induced by vaccination, that that should dampen down infection within you, and therefore prevent these variants from piling up.”

The more people mix with each other, the more likely it is for the virus to spread.

Asked whether delaying relaxing lockdown restrictions would be an effective way to do this, he said: “From a scientific, virological perspective, it makes sense because I guess we all knew that these variants would be popping up, but what’s surprising is, is the nature of some of those variants.”

Rowland Kao, the Sir Timothy O’Shea Professor of Veterinary Epidemiology and Data Science at the University of Edinburgh, said the combination of many infections, plus many vaccinated people, is the most likely circumstance for an “escape mutant” variant to arise.

He added: “These are conditions which we are entering now, as the number of vaccinated individuals increases.

“This is a natural consequence of any vaccination programme and thus requires continued vigilance and surveillance (via the work of Cog-UK (the Covid-19 Genomics UK consortium)) for the emergence of such variants.

“Of course the number of infected and vaccinated around the globe is far higher than the number within the UK, so it is far more likely that such new variants of concern will arise elsewhere than here, thus motivating the requirement for new travel restrictions.”

Prof Young said that regardless of what happens with coronavirus variants, they all spread the same way, and as the main source of transmission is person to person, if you restrict that transmission, you can stop it spreading.

He explained that looking at other countries which are managing the virus effectively would suggest that once case numbers drop to about 1,000 a day, it becomes a more manageable level in terms of pressure on the NHS and deaths.

He added that lockdown restrictions would have to be eased in a staggered way.

“It’s not going to be a big bang,” said Prof Young.

“It’s going to be a gradual incremental easing of lockdown and doing it in a very careful way.

“A very judicious approach to this would say: ‘Let’s stagger this, probably to get the schools back on as much as possible, open up some of the hospitality.’

“We’re going to have to keep social distancing measures, and where appropriate face masks etc, for a long time anyway,” he added.

Prof Young said he thought measures would have to be eased in incremental phases, and the effects looked at every few weeks.

He told the PA news agency: “I think the issue is making sure that we don’t make the mistakes of last year, where we end up with a bit of a freefall over the summer and we live with the consequences over the autumn.”

Dr Alexander Edwards, associate professor in biomedical technology at the University of Reading, said: “Public health control measures are harder, more expensive, and spread more thinly as the volume of cases increases.

“For testing and contact tracing, it’s far more likely to succeed if you have very few new cases daily.

“Identifying important mutants is even harder than normal test and contact tracing (sequencing and mutation analysis is harder than testing alone), so it becomes even more critical to keep case numbers as low as possible.”