New Covid variants: How many strains are in circulation and on the rise around the world?

The UK suffered its fifth wave of Covid-19 infections this summer, with daily cases soaring to 4.6m by mid-July, after which they fortunately began to fall away.

The latest onslaught by the virus first became apparent in the aftermath of the four-day public holiday to celebrate the Queen’s Platinum Jubilee when a 43 per spike in coronavirus cases was reported and it was feared that other major summer gatherings like Notting Hill Carnival and the Edinburgh Festival could all amount to super-spreader events if proper precautions are not taken.

While that did not quite materialise and cases fell to just 120,000 by mid-August, according to the ZOE Health Study, the spike was a timely reminder to stay vigilant.

That surge was driven by the BA.4 and BA.5 sub-variants of Omicron, the strain that spread rapidly across the UK in December 2021 and January 2022 before gradually falling away.

These latest incarnations were first discovered in South Africa in January and February respectively and are effectively the grandchildren of Omicron.

They feature three mutations to their spike proteins, which, it is feared, enable them to retrain their attack on human lung cells.

That means they have more in common with the earlier, more dangerous Alpha and Delta variants than the highly transmissible but milder Omicron, which targeted upper respiratory tract tissue.

Potentially, these mutations might also enable the sub-variants to sidestep antibodies from past infections or vaccination and therefore overcome immunity.

Preliminary data captured by Professor Kei Sato of the University of Tokyo in Japan appears to indicate as much, prompting the virologist to comment: “Altogether, our investigations suggest that the risk of [these] Omicron variants, particularly BA.4 and BA.5, to global health is potentially greater than that of original BA.2.”

While immunity is high in Britain, with 87.9 per cent of the population having had two vaccine doses and 69.1 per cent of people having received a booster jab, the public has largely behaved as though the pandemic never happened since the last of the government’s unpopular restrictions were repealed a month ahead of schedule on 24 February, abandoning face masks and distancing and returning to life as normal.

However, it is now more than eight months since the last major booster jab drive was mounted ahead of Christmas and the New Year and immunity could be beginning to wane, potentially leading to more patients needing professional care and perhaps even deaths, either now or later in the year when flu season descends.

Professor Adam Finn, a member of the government’s Joint Committee on Immunisations and Vaccinations, has already called for a new round of booster jabs to be made available by September.

“The booster protection does fade, particularly against milder infection and after a while against severe infection as well. So that’s a disappointment for us all with regards to these vaccines which have otherwise been very valuable in terms of the pandemic,” he told BBC Radio 4’s Today programme.

“But we are going to need to provide boosters, particularly to people who are at risk getting very seriously ill if they get it later in the year.”

The World Health Organisation (WHO) has been monitoring those strains since April and currently Omicron, including its sub-variants BA.1, BA.2, BA.3, BA.4, BA.5 and descendent lineages, is the only form of Covid that it recognises as a “variant of concern”.

Mercifully, variants previously in that category such as Alpha (formerly known as B.1.1.7 and first detected in Kent), Beta (formerly B.1.351, from South Africa), Delta (B.1.617.2, India) and Gamma (P.1, Brazil) have been relegated from the list and are not, at present, believed to pose a threat.

Others once under scrutiny, like the Epsilon, Eta, Iota, Kappa, Lambda, Mu, Theta and Zeta variants, no longer even make the WHO’s “variants of interest” list.

The European Centre for Disease Prevention and Control likewise lists the same Omicron sub-variants of concern, with the exception of the BA.3 strain, which it has de-escalated to monitoring status only.

In the US, the Centres for Disease Control and Prevention (CDC) currently only lists the same sub-variants as being “of concern” but does keep Alpha, Beta, Delta, Epsilon, Eta, Gamma, Iota, Kappa, Mu and Zeta on record as “variants being monitored”.