Japan's health ministry said on Sunday it had detected a new variant of COVID-19 in four travelers from Brazil's Amazonas state which featured 12 mutations, including one also found in highly infections variants discovered in Britain and South Africa.
"We are concerned about the new Brazilian variant ... and we're taking steps (to protect the country) ... in respect of the Brazilian variant," Johnson told a parliamentary committee.
"I think it's fair to say that there are lots of questions we still have about that variant."
Johnson went on to say that there were 70% more patients in hospital with COVID-19 than at the peak in April last year.
He said the strain on the NHS was "colossal".