DOVER, England—More countries closed their borders to Britain on Monday over fears of a highly infectious new coronavirus strain, heightening global panic, causing travel chaos and raising the prospect of UK food shortages just days before the Brexit cliff edge.

Travellers with suitcases sit at the Eurostar terminal at St Pancras International, as EU countries impose a travel ban from the UK following the coronavirus disease (COVID-19) outbreak, in London, Britain, on Dec. 21, 2020. Hannah McKay/Reuters