A travel ban is to be imposed on six African nations due to rising concerns over a new variant of the virus which causes Covid-19 which officials have dubbed “the worst one we’ve seen so far”.

UK officials sounded the alarm on Thursday night over the B.1.1.529 variant, which has the potential to evade immunity built up by vaccination or prior infection.

Health Secretary Sajid Javid said the new variant identified in South Africa “may be more transmissible” than the Delta strain and “the vaccines that we currently have may be less effective”.

He said that flights 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.

While no cases have been found in Britain, officials raised concern over a rapid rise in cases in South Africa.

Anyone who has arrived from the country in the last 10 days will be invited to come forward and take a test by the UK Health Security Agency.

At the moment, around 500 and 700 people are travelling to the UK from South Africa each day, but it is expected this figure could increase as the festive period begins.

Mr Javid said: “The early indication we have of this variant is it may be more transmissible than the Delta variant and the vaccines that we currently have may be less effective against it.

“Now to be clear, we have not detected any of this new variant in the UK at this point in time.

“But we’ve always been clear that we will take action to protect the progress that we have made.

Bournemouth Echo: Graphic from PAGraphic from PA

“So what we will be doing is from midday tomorrow we will be suspending all flights from six, southern African countries and we will add in those countries to the travel red list. Those countries are South Africa, Namibia, Lesotho, Eswatini, Zimbabwe and Botswana. We will be requiring anyone that arrives from those countries from 4am on Sunday to quarantine in hotels.

“If anyone arrives before then they should self-isolate at home and take a PCR test on day two and day eight. If anyone has arrived from any of those countries over the last 10 days, we would ask them to take PCR tests.”

The variant has not yet been given the title “variant of concern” in the UK, but one senior UK Health Security Agency (UKHSA) expert said: “This is the worst variant we have seen so far.”

Only 59 confirmed cases have been identified in South Africa, Hong Kong and Botswana.

The variant has over 30 mutations – around twice as many as the Delta variant – which could potentially make it more transmissible and evade the protection given by prior infection or vaccination.

Experts from the UKHSA have been advising ministers on the issue.

A number of scientists have expressed serious concern over the variant due to the significant number of mutations in the spike protein.

One senior scientist said: “One of our major worries is this virus spike protein is so dramatically different to the virus spike that was in the original Wuhan strain, and therefore in our vaccines, that it has a great cause of concern.”

Experts from the World Health Organisation (WHO) are meeting with South African officials on Friday to assess the evolving situation in the country.

The variant could eventually be given the moniker “Nu” – with the most concerning variants given named after the Greek alphabet.