The UK has detected two cases of another new variant of coronavirus, the health secretary Matt Hancock says. The cases in London and north west England are contacts of people who travelled to South Africa, where the variant was discovered. Travel restrictions with South Africa have been imposed. Anyone who has travelled there in the past fortnight, and anyone they have been in contact with, are being told to quarantine immediately. The variant has been causing mounting concern in South Africa, where health minister Zweli Mkhize warned that “young, previously healthy people are now becoming very sick”. This variant shares some similarities to the one that has already been detected in the UK, although they have evolved separately. Both have a mutation – called N501Y – which is in a crucial part of the virus that it uses to infect the body’s cells. Prof Neil Ferguson, from Imperial College London, said: “I think the greatest concern of ours at the moment is the South African one. South Africa has so far recorded about 950,000 cases and more than 25,000 deaths – the highest in Africa.