“Assume that it’s here already”

The United Kingdom has identified a new, potentially more contagious coronavirus variant linked to a recent surge in cases in England.

The new mutation is being called VUI-202012/01 – the first “Variant Under Investigation” in the UK in December 2020. While scientists hunt for more information about the variant, its impact is already being felt, with dozens of countries imposing restrictions on travelers from the UK.

Here’s what you need to know:

What is a variant and why are officials concerned about this one? A variant occurs when the genetic structure of a virus changes. All viruses mutate over time and new variants are common, including for the novel coronavirus.

Like other variants, this one carries a genetic fingerprint that makes it easy to track, and it happens to be one that is now widespread in southeast England. That alone does not necessarily mean a variant is more contagious or dangerous.

But scientists advising the UK government have estimated that this variant could be up to 70% more effective at spreading than others. Peter Horby, chair of the New and Emerging Respiratory Virus Threats Advisory Group (NERVTAG), said Monday that experts “now have high confidence that this variant does have a transmission advantage” over other variants.

The World Health Organization said Tuesday that the changes to the variant include 14 key mutations, and that some of them “may influence the transmissibility of the virus in humans,” though it added that further laboratory investigations were needed.

Where did the variant originate and how has it taken hold? The new variant is believed to have originated in southeast England, according to the WHO. Public Health England (PHE) says backwards tracing, using genetic evidence, suggests the variant first emerged in England in September. It then circulated in very low levels until mid-November.

Chris Whitty, England’s chief medical officer, said Saturday the variant was responsible for 60% of new infections in London, which have nearly doubled in the last week alone.

Multiple experts have also suggested that this new variant could have been amplified because of a superspreader event, meaning the current spike in cases could also have been caused by human behavior.

Which countries are affected? The variant has already spread globally. As well as the UK, the variant has also been detected in Denmark, Belgium, the Netherlands and Australia, according to the WHO.

Australia has identified two cases of the variant in a quarantined area in Sydney and Italy has also identified one patient infected with the variant.

A similar but separate variant has also been identified in South Africa, where scientists say it is spreading quickly along coastal areas of the country.

Learn more about the UK coronavirus variant here.