A mutated strain of Covid-19 currently spreading in the UK was detected in Brazil last April.

The variant is reported to be highly-infectious, with numerous cases reported in the UK, Denmark and Italy recently, but scientists say it was spotted last spring in Brazil, and then reported in Australia and the US throughout the summer.

The N501Y mutation has prompted the British government to introduce Tier 4 lockdown restrictions as Christmas approaches, with the Irish government among other European nations and India temporarily banning travel from mainland Britain.

Some experts have suggested young people could be more affected by the variant, whilst others have questioned the scientific evidence informing ministerial decisions on the matter, claiming no reason exists thus far to believe the impact of the variant will be more severe on patients.

Speaking to the Daily Mail, German virologist Christian Drosten said the new strain might not be responsible for the increased number of cases.

“The question is – was it the virus’s fault, or was it simply that in the area where this virus happened to be… methods of transmission came into play which would have brought any other virus to the surface?,” he asked.

“If you want to know if a virus is more transmissible, you’ve have to look at pairs of people who were infected. You’d have to see who infected whom and how long it took,” he said.

Denmark and Australia both detected cases of the mutation last month, with Iceland, the Netherlands and Belgium also finding the strain this month in several positive cases, but Drosten points out that most of those countries have not reported a surge.

The N501Y mutation is reported to be one of 23 separate variants of the latest strain of Covid-19, as scientists race to find out if it’s transmissibility is responsible for Britain’s increased number of cases, with places like Sussex experiencing a five-fold increase in case numbers over the last fortnight.

Prof Neil Ferguson, who was previously criticised for breaking the original lockdown rules his now-refuted work prompted, told BBC Radio 4 that the mutation’s impact on children would have to be studied and the only way to “relax restrictions” was with the vaccine.

“So undoubtedly increased transmissibility limits our options for manoeuvre even more, and there is a hint from the data that this variant may infect children slightly more effectively than the previous variants, so it’s very difficult to prove causality.

“I think what we’ll see in the next two weeks though, whilst schools are closed, is probably all the variants of the virus in circulation at the moment declining, we’ll be tracking very carefully whether we can see differences in that rate of decline and really it’s the data which is being put together now and unfortunately over the Christmas break which is going to inform policy measures in January.

“The faster we can get the vaccine into people’s arms, the quicker we’ll be able to, not go back completely to normal, but at least to be able to relax restrictions.

“The Government gets criticised for changing policy all the time, this virus is unpredictable, how people behave is unpredictable, and so we will track the epidemic as we always have done and policy will be formed on the basis of that.”