(THE HILL) — The announcement of a COVID-19 variant called B.1.1529 this week by scientists in South Africa, where it was first detected, has sent governments and financial markets around the world reeling.

The World Health Organization (WHO) held an emergency meeting on Friday, where it designated the new strain, which it called omicron, a “variant of concern,” or VOC, a label applied when a particular strain is especially virulent, transmissible or able to defeat public health measures.

The Dow Jones Industrial Average suffered its worst single-day drop of the year, plummeting more than 900 points.

And multiple nations, including the U.S., quickly imposed travel restrictions as the omicron variant was also detected in Israel, Hong Kong, Botswana and Belgium.

Infectious disease expert Anthony Fauci said Friday the U.S. is “rushing” to obtain information on B.1.1529, but emphasized there is not enough data for immediate action.

Here’s what you should know about omicron.

U.S. restricts travel to southern Africa

U.S. senior administration officials said Friday the U.S. would restrict travel to eight African countries starting Monday due to the variant. 

The countries affected are South Africa, Botswana, Zimbabwe, Namibia, Lesotho, Eswatini, Mozambique and Malawi.

Officials say the move was made out of an “abundance of caution” and was recommended by U.S. government medical experts and the COVID-19 Response Team. The restriction does not apply to American citizens or lawful permanent residents. 

Fauci said in an interview with CNN Friday U.S. and South African scientists will have a meeting regarding the new variant and its molecular makeup.

Although Fauci says no cases have been detected so far in the U.S., he added scientists need more information on the variant’s molecular makeup to test for it. 

“Right now, we’re getting the material together with our South African colleagues to get a situation where you could actually directly test it. So, right now you’re talking about sort of like a red flag that this might be an issue — but we don’t know,” Fauci said.

“Once you test it, you’ll know for sure whether or not it does or does not evade the antibodies that we make — for example against the virus, through a vaccine,” he added. “The answer is we don’t know right now, but we’re going to find out for sure.”

Omicron has a high number of mutations

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

Tulio de Oliveira, a bio-informatics professor at two universities in South Africa, said during the press conference there Thursday the new variant is “clearly different” than past ones such as delta.

De Oliveira said at least 50 B.1.1529 mutations have been identified, with more than 30 in the spike protein, the region that interacts with human cells prior to cell entry.

Fauci said in an interview with CNN on Friday the variant is spreading at “a reasonably rapid rate.”

One hundred new cases so far have been linked to the B.1.1529, said Anne von Gottberg, a clinical microbiologist and head of respiratory diseases at the National Institute for Communicable Diseases. 

Although it is unclear whether the current coronavirus vaccines will be as effective against the new variant, many scientists appear confident they will, as was the case for other variants such as the highly contagious delta. 

Spike protein leads to concerns

A particular concern in the new variant are the mutations affecting the spike protein, which could potentially make it more contagious.

Fauci told the outlet the mutations in the spike protein “are raising some concern, particularly with regard to possibly transmissibility increase, and possibly evasion of immune response.”

The U.K. Health Security Agency has also recognized the potential for the mutations in the spike protein to make the variant more transmissible; however, more evidence is needed to support the conclusions.

First found in South Africa, but now appearing elsewhere

The first case of the B.1.1529 variant was detected in South Africa, which has struggled to contain the coronavirus along with its ongoing AIDS/HIV concerns.

Francois Balloux, director of the UCL Genetics Institute, said the new variant likely developed in an immunocompromised person since the virus can last longer than normal in those individuals.

It is possible the variant occurred in an individual who was untreated for AIDS/HIV, as South Africa has the world’s highest AIDS rate. 

The number of cases rapidly increased in South Africa as only 100 were found earlier this month and more than 1,200 cases in the country were known as of Wednesday, Axios reported.

As a result, at least 10 countries have banned travel from southern African regions in an attempt to keep the virus from spreading. 

Cases, however, have already been identified in Europe and Eastern Asia.

It is tanking markets

The announcement of the new variant has tanked markets across the world as concerns rise on how much longer the B.1.1529 could make the pandemic last. 

On Friday, the Dow Jones Industrial Average fell 900 points with stocks in oil, technology and electric vehicle companies dropping significantly. 

Japan’s Nikkei and China’s Hang Seng index each fell by 2 percent as countries move to restrict travel.