Travel stocks tumbled in premarket trading, RCL and CCL shares were down more than 12%.
Britain said on Friday that a newly identified coronavirus variant spreading in South Africa was considered by scientists to be the most significant one yet found and so it needed to ascertain whether or not it made vaccines ineffective.
Defending a ban on flights from South Africa, Namibia, Botswana, Zimbabwe, Lesotho and Eswatini, Transport Secretary Grant Shapps said that the lesson of COVID was that early action was essential.