Researchers have identified a hybrid Omicron XE coronavirus variant that may be as much as 10 per cent more transmissible than earlier variants.
Several countries have reported the Omicron XD and XF hybrid variants, recombinants of Delta and Omicron.
The latest variants are likely to be contributing to surging Covid infection numbers in the UK. A record 4.9 million people in Britain are estimated to have had Covid-19 in the week ending March 26, up from 4.3 million on the week before, the Office for National Statistics said.
Experts are uncertain about whether the new variants produce more severe symptoms in highly vaccinated populations.
Britain's white-collar workers are not hedging their bets, however, with offices emptying rapidly because of high levels of sickness and a desire to avoid infection.
Craig Beaumont, chief of external affairs at the Federation of Small Businesses, told the Financial Times that one in seven UK businesses were operating at a reduced capacity because of sickness.
“Having brought more people back to the workplace, bosses are now increasingly worried at having more Covid-19 there, too,” he said.
“In the face of such disruption, this is the wrong time for the government to withdraw free testing and downgrade safer workplace guidance.”
What are the new Omicron hybrid variants?
The UK Health Security Agency is monitoring three hybrid variants: XD, XE and XF.
Omicron XD variant
Most concern is centred round the XD variant, which is a recombinant sublineage of Delta and Omicron BA.1.
It was first detected in December, with 22,490 samples found by March 22 in France, Denmark and Belgium.
“The concern would be if there are non-structural changes in Delta that contribute to severity and/or cell replication,” virologist Tom Peacock from Imperial College London wrote on Twitter.
Omicron XE variant
Omicron XE is a combination of Omicron BA.1 and BA.2 but with three separate and distinct mutations. It has only been found in Britain to date but the UK Health Security Agency has suggested it could be nearly 10 per cent more transmissible than its parents.
So far, 637 XE cases have been identified in the UK, but the true figure is likely to be much higher as the UK has abolished free tests and reduced testing infrastructure.
Prof Susan Hopkins, the UK Health Security Agency's chief medical adviser, said that so far, little was known about XE.
“There is not enough evidence to draw conclusions about transmissibility, severity or vaccine effectiveness,” she said.
Omicron XF variant
XF is a combination of Delta and BA.1 and has only been found in Britain.
Of the three sublineages, it is of the least concern to scientists, with no cases identified since February 14.