The World Health Organization on Friday assigned the Greek letter Omicron to a newly identified Covid variant in South Africa.

The U.N. health agency recognized the strain, previously referred to as  lineage B.1.1.529, as a variant of concern.

Health experts are  deeply concernedabout the transmissibility of the Omicron variant given that it has an unusual constellation of mutations and a profile that is different from other variants of concern.

&ldquo This variant has a large number of mutations, some of which are concerning,&rdquo the WHO said in a statement released Friday. &ldquo Preliminary evidence suggests an increased risk of reinfection with this variant, as compared to other VOCs.&rdquo  

It is feared a sharp upswing of Covid cases in South Africa&rsquo s Gauteng province &mdash where the heavily mutated strain of the virus was first identified &mdash could mean it has greater potential to escape prior immunity than other variants. The number of Omicron cases &ldquo appears to be increasing&rdquo in almost all of South Africa&rsquo s provinces, the WHO reported. 

The designation of a new variant of concern coupled with mounting alarm from health officials  sent global markets into a tailspin on Friday. Oil prices and travel and leisure stocks took heavy losses on the news.

To be sure, WHO has said it will take weeks to understand how the variant may impact diagnostics, therapeutics and vaccines.

South African scientist Tulio de Oliveira said at a media briefing on Thursday that the Omicron variant contains around 50 mutations, but more than 30 of these are in the spike protein, the region of the protein that interacts with human cells prior to cell entry.

What&rsquo s more, the receptor binding domain (the part of the virus that first makes contact with our cells) has 10 mutations, far greater than just two for the delta Covid variant, which spread rapidly earlier this year to become the dominant strain worldwide.

This level of mutation means it most likely came from a single patient who could not clear the virus, giving it the chance to genetically evolve. The same hypothesis was proposed for the alpha Covid variant.

Around 100 Omicron variant genomes have been identified in South Africa, mostly in the Gauteng province. The variant has also been detected in Israel, Botswana and Hong Kong.

Many of the mutations identified in the Omicron variant are linked to increased antibody resistance, which may reduce the effectiveness of vaccines and affect how the virus behaves with regard to inoculation, treatments and transmissibility,  health officials have said.

&ldquo There are two approaches to what happens next: wait for more scientific evidence &mdash or act now and row back later if it wasn&rsquo t required,&rdquo said Sharon Peacock, professor of public health and microbiology at the University of Cambridge.

&ldquo I believe that it is better to &lsquo go hard, go early and go fast&rsquo and apologise if mistaken, than to take an academic view that we need to reach a tipping point in evidence before action is taken. Rapid spread in South Africa could be due to super-spreader events or other factors. But there are sufficient red flags to assume the worst rather than hope for the best &mdash and take a precautionary approach,&rdquo Peacock said.

The European Union, the U.K., Israel and Singapore are among the countries to have  moved  to impose travel restrictions on southern African nations.

The WHO has cautioned countries against hastily imposing travel restrictions, saying countries should instead take a &ldquo risk-based scientific approach.&rdquo

South Africa&rsquo s foreign ministry said on Friday morning that the U.K.&rsquo s decision to take precautionary measures &ldquo seems to have been rushed as even the WHO is yet to advise on the next steps.&rdquo

&mdash CNBC&rsquo s Elliot Smith contributed to this report.

The World Health Organization will meet on Friday to discuss a new  heavily-mutated variant of Covid-19.

The variant known as B.1.1.529 has been detected in small numbers in South Africa, WHO officials said, with reports on Friday morning of cases being found in Israel and Hong Kong.

Here&rsquo s what we know so far:

South African scientist Tulio de Oliveira said in a media briefing held by the South Africa Department of Health on Thursday that the variant contains a &ldquo unique constellation&rdquo of more than 30 mutations to the spike protein, the component of the virus that binds to cells. This is significantly more than those of the delta variant.

Many of these mutations are linked to increased antibody resistance, which may affect how the virus behaves with regard to vaccines, treatments and transmissibility, health officials have said.

In total, de Oliveira said the variant contains around 50 mutations. The receptor binding domain (the part of the virus that first makes contact with cells) has 10 mutations, far greater than just two for the delta Covid variant, which spread rapidly earlier this year to become the dominant strain worldwide.

This level of mutation means it&rsquo s possible that it came from a single patient who could not clear the virus, giving it the chance to genetically evolve. The same hypothesis was proposed for the alpha Covid variant.