LONDON — British Health Secretary Matt Hancock says scientists have identified another new variant of the coronavirus in two people, both of whom are contacts of recent arrivals from South Africa. Hancock told a press briefing that anyone who has been in South Africa in the past two weeks, together with their close contacts, have to quarantine themselves “immediately.” Hancock said the evidence collated so far suggests that the new variant has “mutated further” than the one that recently prompted the British government to tighten restrictions across large parts of England and which led to