A Brazilian variant of coronavirus that has been detected in the UK is not the mutation that sparked a South American travel ban, it has been confirmed.

Japan’s health ministry said on Sunday it had detected a new strain of the virus in four travellers from Brazil’s Amazonas state that featured 12 mutations – including one also found in highly infections variants discovered in Britain and South Africa.

And Professor Wendy Barclay, head of G2P-UK National Virology Consortium – a new project set up to study the effects of emerging coronavirus mutations – initially said on Friday that one of two known Brazilian variants had been identified in Britain.

She added: “In the databases, if you search the sequences, you will see that there is some some evidence for variants from around the world, and I believe including the Brazilian one, which probably was introduced some time ago.

“And that will be being traced very carefully.”

But Professor Barclay added: “The new Brazilian variant of concern, that was picked up in travellers going to Japan, has not been detected in the UK.

“Other variants that may have originated from Brazil have been previously found.”

A South American travel ban came into force at 4am on Friday to minimise the risk to the UK of the new, potentially more infectious, variant found in Brazil.

Boris Johnson earlier this week struggled to explain the measures that would be brought in.