WHO name Omicron 'variant of concern'
The United States joined the EU and Britain in restriction in and outbound flights from a number of South African countries, following concerns about a new strain of coronavirus, now named Omicron.
The World Health Organisation have classed this strain as a 'variant of concern.'
WHO Covid Technical Lead Dr Maria Van Kerkhove says this is due to this particular variant's mutations.
The WHO have also said Omicron could be more resistant to vaccines.