TRAVELLERS recently arrived from South Africa will be asked to come forward for testing amid alarm over a new variant which scientists consider to be the worst of the pandemic to date. 

The B.1.1.529 strain, which has yet to be formally named, is spreading rapidly in South Africa although Public Health England said it has not yet identified any cases in the UK. 

The new variant has over 30 different mutations – twice as many as the Delta variant – which have produced a dramatically different spike protein than that seen in the original Wuhan strain, which was the basis for vaccine developers. 

These appear to include changes which would enable it to evade immunity from vaccines and prior infection, as well as conferring increased infectivity, increased transmission, and alterations to the cleavage site which the virus uses to ‘break into’ cells. 

Based on its mutations scientists expect that will respond to vaccines similarly to the existing Beta variant. This would mean that the AstraZeneca vaccine provides only 40-50 per cent protection against symptomatic infection, and the Pfizer vaccine only 50-60%, both soon after inoculation with a second dose.

The variant is considered to be the worst so far in the pandemic, due to the sheer number and characteristics of its mutations.

Scientists are extremely worried and consider the variant to be a significant cause for concern, although they stress that at this stage there is no evidence of any change to the UK’s disease epidemiology which would indicate it spreading here.

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."

They added: "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."

The new variant is characterised by a marker known as an S-gene dropout which should enable scientists to track its emergence and spread.

There are already signs that its incidence has increased rapidly in South Africa over a period of weeks, although it still remains at low overall prevalence There are around 500-700 people entering the UK each day from South Africa.

Scientists will be able to gauge its impact on vaccination resistance within around two to eight weeks based on its current rate of spread and the fact that South Africa is a highly vaccinated population.

The World Health Organisation is meeting with South Africa’s Covid experts tomorrow to discuss the situation.

Current surveillance in the UK – which includes sequencing of around 70,000 samples per week, a huge number by international standards – has not detected any cases of the new variant.

However, anyone who has arrived in the UK from South Africa in the past 10 days is expected to be contacted as part of efforts to contain the variant if it has arrived.

The variant could eventually be given the moniker "Nu" - with the most concerning variants given named after the Greek alphabet.

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

Professor Tulio de Oliveira, the director of the Centre for Epidemic Response and Innovation in South Africa, said there was an "unusual constellation of mutations" and that the variant was "very different" to other which have circulated.

"This variant did surprise us, it has a big jump on evolution [and] many more mutations that we expected," he said.

This scale of mutation suggests it evolved in a single infected person with prolonged illness, in a similar way to the emergence of the Alpha variant first linked to a Kent patient.