Omicron: Mutations prompt new coronavirus variant concern from WHO

The World Health Organization (WHO) has declared a new coronavirus mutation a "variant of concern".

The variant, given the name Omicron, was first reported to the WHO from South Africa on 24 November.

Previously known as B.1.1.529, it has also been identified in Botswana, Belgium, Hong Kong and Israel.

The WHO said on Friday that early evidence suggested an increased risk of reinfection with this variant.

In a statement on Friday the organisation said the number of cases of this variant appeared to be increasing in almost all South African provinces. 

"This variant has a large number of mutations, some of which are concerning," it said.

It is not uncommon for a virus to change, or mutate, over time. A variant becomes a variant of concern when that mutation might affect things like transmissibility, virulence or the effectiveness of vaccines.

The WHO has said it will take a few weeks to understand the impact of the new variant, as scientists work to determine how transmissible it is.

It has warned against countries hastily imposing travel restrictions, saying they should look to a "risk-based and scientific approach".

However, the UK, EU countries and Switzerland have temporarily halted flights from some southern African countries.

"It is now important that all of us in Europe act very swiftly, decisively and united," European Commission chief Ursula von der Leyen said.

South Africa's Health Minister Joe Phaahla told reporters that the flight bans were "unjustified".

"The reaction of some of the countries, in terms of imposing travel bans, and such measures, are completely against the norms and standards as guided by the World Health Organization," he said.

Stock markets across the world also fell sharply on Friday, reflecting the fears of investors over the potential economic impact.