South Africa coronavirus variant: What is the risk?

The government's announced it's to carry out door-to-door testing in parts of England for a new variant of coronavirus originally identified in South Africa.

More than 100 cases of the South Africa variant have been spotted since 22 December. Most are linked to travel, but some may be community cases.

Experts are studying the variant to understand what risk it poses.

All viruses, including the one that causes Covid-19, constantly mutate into new versions or variants.

These tiny genetic changes happen as the virus makes new copies of itself to spread and thrive.

Most are inconsequential, and a few can even be harmful to the virus's survival, but some variants can make the virus more infectious or threatening to the host - humans.

There are now many thousands of variants of the pandemic virus circulating. But experts are concerned about the South African variant, or 501.V2.

There is no evidence that the South Africa variant causes more serious illness for the vast majority of people who become infected.

As with the original version, the risk is highest for people who are elderly or have significant underlying health conditions.

But there are concerns it can spread more readily and vaccines may not work quite as well against it.

The South African variant carries a mutation called E484K, among others.

It's different to the recently discovered UK or Kent variant that scientists have also been studying in the UK.

Both variants appear to be more contagious, which is a problem because tougher restrictions on society may be needed to control the spread.

While changes in the new UK variant are unlikely to harm the effectiveness of current vaccines, there is a chance those in the South African variant may do so to some extent, say scientists.

It is too soon to say for sure, or by how much, until more tests are completed, although it is extremely unlikely the mutations would render vaccines useless.

Scientists have tested the Pfizer Covid vaccine against one of the mutations found in the South African variant, called N501Y, using blood samples from 20 people.

In that preliminary study, vaccination appeared to work against the mutated virus.

More studies are needed though.

N501Y is not the only change the South African variant has undergone.

Dr Simon Clarke, who is an expert in cell microbiology at the University of Reading, said: "The South African variant has a number of additional mutations including changes to some of the virus' spike protein which are concerning."

The spike protein is what coronavirus uses to gain entry into human cells. It is also the bit that vaccines are designed around, which is why experts are worried about these particular mutations.

Prof Francois Balloux, from University College London, said: "The E484K mutation has been shown to reduce antibody recognition. As such, it helps the virus SARS-CoV-2 to bypass immune protection provided by prior infection or vaccination."

Early results from Moderna suggest its vaccine is still effective against the South Africa variant, although the immune response may not be as strong or prolonged.

Two new coronavirus vaccines that could be approved soon - one from Novavax and another from Janssen - appear to offer some protection against the variant.

Even in the worst case scenario, vaccines can be redesigned and tweaked to be a better match in a matter or weeks or months, if necessary, say experts.

It is already the dominant virus variant in the Eastern and Western Cape provinces of South Africa.

At least 20 other countries including Austria, Norway and Japan, have also found cases.

Travel is now banned from many countries in southern Africa, as well as Tanzania and Democratic Republic of Congo.

Targeted testing in the community is also taking place in Surrey, London, Kent, Hertfordshire and Walsall. Postcodes affected are:

Public health authorities and scientists are studying the variant and will share their findings soon.