Covid variant Orthrus now accounts for one fifth of Covid cases in England, figures show.
Surveillance data shows how the strain, scientifically called CH.1.1, has snowballed since it was first detected in November.
Health chiefs have warned that it — or another Omicron sub-lineage nicknamed the ‘Kraken’ — could soon become dominant.
The latter, or XBB1.5, has sparked fears it could trigger a Covid resurgence, putting even more pressure on the NHS at a time when it is being battered by its worst ever winter.
Maps, taken from the Sanger Institute, which tracks Covid variants in England using data from genomic testing, show Omicron spin-off Orthrus has spread up and down the nation as of January 7, the latest available data. It now accounts of 23.3 per cent of all Covid test analysed up from 1 per cent on November 12 when it was first spotted in Blaby in the south west of Leicestershire
Data from the Sanger Institute, one of the UK’s largest surveillance sites tasked with analysing strains circulating in the UK, shows Orthrus, nicknamed after a mythical two-headed dog, accounted for 23.3 per cent of all Covid tests analysed in England on January 7, the latest data available.
Fascinating maps show it now accounts for 100 per cent of genomic tests of the virus in some boroughs.
These include Northumberland, Bradford, Wakefield, Blackburn with Darwen, North West Leicestershire, Breckland, Central Bedfordshire, Oxford, Reading, Woking, Enfield, Havering, Sevenoaks, Crawley, and Adur.
It shows how far the new variant has come since when it was first spotted in Blaby in the south west of Leicestershire on November 12.
But the Sanger data is only based on hundreds of samples, meaning it does not reflect the true picture.
The majority of Covid-positive samples are not sequenced by the lab, which was analysing thousands every day during the height of the pandemic.
Kraken, nicknamed after a mythical sea monster, currently accounts for 3.6 per cent of cases in England, according to the same data.
However, it was only spotted in mid-December.
While Orthrus is behind more infections, experts have said Kraken appears to be growing faster and is thought to be more transmissible and immune evasive than other strains in circulation.
UK Health Security Agency data suggested that Kraken has a 39 per cent growth rate advantage over BQ.1, the current dominant variant.
This chart, taken from the Sanger Institute, shows the growth of both Orthrus (salmon colour) and Kraken (purple) since November 12. However, Omicron strain BQ.1 (yellow) is still the dominant variant. Other Covid variants on the chart include other BA.5 sub-lineages (maroon), BA.2 (light blue) and BA.4 (thin orange line)
The latest ONS Covid infection survey shows that 4 per cent of England’s population was infected on any given day last week — a drop from 4.5 per cent last week. In Scotland, levels increased by 3 per cent in Scotland to 219,600, meaning one in 25 people (4.1 per cent of the population) were infected in the week to December 31. Around 157,000 people in Wales (one in 18, 5.7 per cent) were thought to be carrying the virus in the seven days to January 3, down 9.4 per cent in a week. In Northern Ireland, 129,100 people were infected (one in 14, 7 per cent) — an increase of 9.3 per cent. However, the ONS said the weekly trend is uncertain
COVID: The number of people infected with Covid taking up hospital beds in England fell 11 per cent from 9,414 in the week to January 4 to 8,404 in the seven days to January 11. NHS data shows the figure peaked at 9,533 on December 29 and has since fallen 19 per cent to 7,743
Meanwhile, the advantage rate for Orthrus was 22 per cent.
However, the UKHSA cautioned Kraken’s current low prevalence in the UK makes any estimate of its growth ‘highly uncertain’.
Neither Covid variant has been escalated to being declared a ‘variant of concern’ by the UKHSA.
This suggests there are no signs they cause more severe disease than other, similarly mild Omicron strains, nor are sufficiently genetically divergent as to cause Covid vaccines to be less effective.
However, scientists have found both host concerning genetic quirks.
Orthrus has a mutation called P681R — which was also on the Delta variant — and is thought to make it better attack cells and cause more severe illness.
Scientists have also spotted it has R346T, which is thought to help the strain fight-off antibodies that were generated in response to vaccination or previous infection.
And Kraken has one called F486P, which helps it to bypass Covid-fighting antibodies. Another mutation — S486P — is thought to improve its ability to bind to human cells.
Concerns over the two new strains, combined with the unfolding NHS crisis and a ‘flu-nami’, has triggered calls for the return of pandemic-era restrictions like masks and working-from-home in a bid to ease pressure on the ailing health service.
But the latest data from the Office of National Statistics (ONS) suggests Covid cases have actually fallen in England.
According to the data, 2.2million people, or one in 25 people, were infected with the virus in the week to January 3.
ONS analysts estimated that the total was 11 per cent lower than the week before.
However, as many as one in 14 people were still infected in the worst-affected parts of the UK.
And some have suggested it could be the calm before another wave of infections.
Data for England showed cases fell in all regions apart from the North East, where 4.1 per cent of people were infected — up from 3.8 per cent one week earlier.
Infections were highest in the East Midlands, South West and South East, where 4.5 per cent were thought to be carrying the virus.
Cases were lowest in London and the North West, where 3.5 per cent were infected, according to ONS estimates.
But the ONS, which swabs thousands of people across the UK to estimate how prevalent the virus is, noted that these estimates are based on a lower than usual number of swabs due to the festive period.
Warnings about the new variants also came as the number of people infected with Covid taking up hospital beds in England is falling.
The figure dropped 11 per cent from 9,414 in the week to January 4 to 8,404 in the seven days to January 11.
NHS data shows Covid patients peaked at 9,533 on December 29 and has since fallen 19 per cent to 7,743.
Just one in three so-called Covid patients are primarily admitted to hospital because of the virus. The remaining two-thirds were taken into NHS care for another ailment, such as a broken leg, but happened to test positive.
If the downwards trend continues, it means the wave will have peaked below 10,000, which is well below the figures seen in previous waves.
The number topped 14,000 during summer 2022 and reached 17,000 last winter.