Camilla Jessen
A new Covid variant called Stratus is now dominant in England.
A new Covid strain called ‘Stratus’ is spreading fast across the UK and has now become the dominant variant, prompting concern among health officials and scientists.
Official data from the UK Health Security Agency (UKHSA) shows that the variant, officially known as XFG, has jumped from just 10% of Covid cases in May to nearly 40% by mid-June.
What Makes Stratus Different?
Stratus is a recombinant strain—often referred to as a ‘Frankenstein’ variant—meaning it was created when someone was infected with two different strains at the same time.
This hybrid evolution has resulted in mutations that make Stratus more infectious and better at dodging the body’s immune defenses.
Professor Lawrence Young, a virologist at Warwick University, told MailOnline that both the main variant XFG and its offshoot XFG.3 are spreading quickly due to new mutations in the virus’s spike protein.
“These variants are more able to evade the immune response,” he said.
Waning Immunity Raises Infection Risk
With fewer people getting booster shots and overall Covid cases down in recent months, experts worry that public immunity is slipping.
According to Professor Young, this dip in protection may leave more people vulnerable to catching the virus, especially the new XFG strains.
“This could lead to a new wave of infection,” he said, though it remains unclear how large that wave might be.
Is Stratus More Dangerous?
So far, there’s no indication that Stratus causes more severe illness than other recent variants.
Vaccines still offer strong protection against hospitalisation and serious outcomes, according to current assessments.
Still, its rapid rise has caught the attention of global health bodies.
WHO Is Now Monitoring Stratus
The World Health Organization (WHO) has officially designated Stratus as a “variant under monitoring,” meaning countries are being asked to keep a close watch on its spread.
While WHO currently rates the overall risk as low, they acknowledge that the variant is growing significantly faster than others.
Globally, Stratus now accounts for around 22% of recorded Covid cases.
A Second Variant Also Rising: Nimbus
Stratus isn’t alone. Another variant named Nimbus has also seen a surge in cases, jumping from just 2% in April to 17% in June.
Like Stratus, Nimbus isn’t believed to bring new symptoms, but doctors have warned of a particularly sharp sore throat—described as a “razor blade” feeling—as a common complaint.
Swollen neck glands have also been reported.
Dr Michael Gregory of NHS England in the North West has noted that Nimbus appears to be “spreading rapidly within communities.”
Covid Cases Falling—But Not Time to Relax
Despite these new variants, the UK is seeing an overall drop in Covid cases.
As of the last week of June, only 5.4% of Covid tests came back positive, down from 7% the previous week.
That 7% figure was the highest positivity rate this year.
However, health experts caution against complacency.
While newer strains don’t seem deadlier, the virus still poses serious risks to older adults and those with weakened immune systems.
No Drastic Symptoms, But Risk Remains
Neither Stratus nor Nimbus is causing drastically new symptoms, but any infection can still lead to complications—especially in vulnerable populations.
Health officials continue to advise vaccination as the most effective way to guard against severe outcomes.
As the virus continues to evolve, keeping an eye on symptoms like persistent sore throat or swollen glands remains key, especially for people in high-risk groups.
