Also on Friday, the Belgian government said that one individual who had recently arrived from abroad, and was not vaccinated, had tested positive for the new variant, marking the first case in Europe.

Tulio de Oliveira, the director of South Africa’s Center for Epidemic Response and Innovation, said the variant has “many more mutations than we have expected,” adding it is “spreading very fast and we expect to see pressure in the health system in the next few days and weeks.”

Viruses, including the one that causes Covid-19, mutate regularly and most new mutations do not have significant impact on the virus’s behavior and the illness they cause.

The World Health Organization (WHO) will hold a meeting on Friday to decide whether the B.1.1.529 variant should be considered one “of interest” or “of concern,” designations that signify the amount of risk that it could pose to global public health. WHO added it would “share further guidance for government on actions they can take.”

What we know about the new variant

Lawrence Young, a virologist and a professor of molecular oncology at Warwick Medical School in the United Kingdom, said the variant was “very worrying.”

“It is the most heavily mutated version of the virus we have seen to date. This variant carries some changes we’ve seen previously in other variants but never all together in one virus. It also has novel mutations,” Young said in a statement.

Neil Ferguson, the director of the MRC Centre for Global Infectious Disease Analysis at Imperial College London, said in a statement that the number of mutations on the spike protein was “unprecedented.”

“The spike protein gene [is] the protein which is the target of most vaccines. There is therefore a concern that this variant may have a greater potential to escape prior immunity than previous variants,” Ferguson said.

Sharon Peacock, a professor of Public Health and Microbiology at the University of Cambridge, said that while the overall number of Covid-19 cases is relatively low in South Africa, there has been a rapid increase in the past seven days.

She said that while 273 new infections were recorded on November 16, the figure had risen to more than 1,200 cases by November 25, with more than 80% coming from Gauteng province.

“The epidemiological picture suggests that this variant may be more transmissible, and several mutations are consistent with enhanced transmissibility,” Peacock said in a comment shared by the UK’s Science Media Centre.

She added that while the significance of the mutations and their combination is unknown, some of those present in the latest variant have been associated in others with immune evasion.

What we don’t know

Peacock, de Oliveira, Ferguson and other scientists said it was too early to tell the full impact of the mutations on vaccine efficacy.

De Oliveira stressed that the shots are still the best tool against the virus, adding that lab studies still need to be carried out to test vaccine and antibody evasion.

More studies also need to be conducted to understand the clinical severity of the variant compared to previous variants.

It is also unclear where the new mutation emerged from. While it was first identified in South Africa, it may have come from elsewhere.

“It is important not to assume that the variant first emerged in South Africa,” Peacock said.

Quick reaction

Scientists have praised South African health authorities for their quick reaction to a Covid-19 outbreak in the country’s Gauteng province, which led to the discovery of the new variant.

When cases in the province started to rise at a higher rate than elsewhere, health experts focused on sequencing samples from those who tested positive, which allowed them to quickly identify the B.1.1.529 variant.

Peacock said the South African health ministry and its scientists “are to be applauded in their response, their science, and in sounding the alarm to the world.”

She added that the development shows how important it is to have excellent sequencing capabilities and to share expertise with others.

UK officials announced on Thursday that six African countries will be added to England’s travel “red list” after the UK Health Security Agency flagged concern over the variant.

UK’s Health Minister Sajid Javid said flights to the UK from South Africa, Namibia, Lesotho, Botswana, Eswatini and Zimbabwe will be suspended from midday Friday and all six countries will be added to the red list — meaning UK residents and British and Irish nationals arriving home from those points of departure must undergo a 10-day hotel quarantine at their own expense.

Speaking on Friday, Javid said it was “highly likely” that the B.1.1.529 variant has spread beyond southern Africa. In a statement to the UK House of Commons Friday Javid expressed concern that it may “pose a substantial risk to public health.”

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, told CNN on Friday that the United States will make a decision as quickly as possible on blocking travel from some African countries in the light of the new variant.