The fast-spreading and new variant of the coronavirus in the UK has prompted more than a dozen countries to ban travel from Britain.

The seemingly fast-spreading and new variant of the coronavirus in the UK has prompted more than a dozen countries to ban travel from Britain. But we still don’t know that this variant is indeed more contagious, according to news reports.

Over the weekend, U.K. officials announced a lockdown on London and parts of southeastern England after evidence emerged that a variant of SARS-CoV-2 (the virus that causes COVID-19) was up to 70% more contagious than other variants, according to The New York Times. By Monday (Dec. 21), some 40 countries had banned entry from the U.K., The Times reported. That estimate comes in part from the fact that the virus had replaced other, long-circulating variants to become dominant, according to The Times.

New variants of SARS-CoV-2 — caused by mutations in the virus’s genetic material — are not surprising and occur quite frequently, Live Science previously reported. But officials are concerned about the new variant in part because of how quickly it seemed to take off and become the dominant variant in the area.

The variant was first detected in the U.K. in September, according to the BBC. By November, it was responsible for about one-quarter of new COVID-19 cases in London, and by mid-December, it was responsible for nearly two-thirds of cases, according to the BBC. A similar variant was found in South Africa, and now accounts for 80% to 90% of new cases in the region, The Times reported.

“We normally see 20 to 30 lineages in our samples at a given time,” Tulio de Oliveira, a professor at the University of KwaZulu-Natal’s Nelson R. Mandela School of Medicine, in South Africa, told The Times. “Now, we see only one.”

Still, it’s possible that this variant became more common simply by chance, rather than due to some inherent advantage of the virus, the BBC reported. Laboratory experiments will be needed to confirm whether it is indeed more transmissible. So far, the variant does not appear to cause more severe or deadly illness than other variants.

The new variant has 17 new genetic alterations compared with previous variants, including some mutations in the infamous “spike protein,” which allows the virus to bind to the ACE2 receptor and infect human cells. In theory, such mutations could allow the virus to spread more easily. For example, one of the mutations is in the so-called receptor-binding domain, the site where the virus first docks with human cells, and this may make the virus “sticker,” or allow it to bind more tightly to human cells.

“The way that I like to think of it is that it’s a little bit more sticky than the COVID virus that we’ve been seeing to date,” Dr. Mark Ghaly, secretary of the California Health and Human Services Agency said in a news conference about COVID-19 on Monday (Dec. 21).

But it’s unlikely that the mutations will render COVID-19 vaccines less effective, at least in the near-term. That’s because the two vaccines that have approval prompt the immune system to make antibodies to a number of sites on the coronavirus, so even if a mutation develops in one spot, there are still antibodies that target other sites, Live Science previously reported.

Originally published at Live Science