The new Delta variant strain AY.4.2 now accounts for around 12% of cases in the UK, according to a recent study, and is thought to be 15% more infectious than other strains
Image: Daily Mirror/Andy Stenning)
A more infectious strain of Covid-19 which may cause less symptomatic cases is spreading across the UK.
The Delta variant strain AY.4.2 accounted for around 12% of samples gathered in a recent government study, which ran up to November 5.
Cases of the sub-variant were growing at 2.8% a day, meaning it was spreading quickly across the UK.
It is thought to be 10 to 15% more infectious than other Delta variants, paving the way for it to become the dominant strain in the UK in several months.
On a more positive note, early research suggests that it may be less likely to cause symptomatic cases than previous iterations.
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Scientists at Imperial College London found that 66.7% of AY.4.2 cases were symptomatic, compared to 76.4% of its Delta parent, AY.4.
Symptoms such as loss or change of smell or taste, a fever, or a new persistent cough appeared in a third of AY.4.2 cases, while the number stands at 46.3% of AY.4 original Delta strain cases.
The new sub-variant also doesn’t seem to make vaccines any less effective.
Christl Donnelly, professor of statistical epidemiology at Imperial College London, believes the new strain is more infectious than the common Delta variant.
He said: “It is absolutely the case that if people are waiting for symptoms to do a test and to therefore identify that they are infected, and therefore cut back their contacts, being asymptomatic may facilitate transmission for example.
“It is an asymptomatic transmission that really can make the difference between what’s relatively easily containable and what needs vaccination.”
Researchers have warned that it’s too early to say for sure whether the new sub-variant is really less likely to make people sick.
It may be that other factors are at play, such as more of the cases being recorded in young people who are less likely to fall ill, or those who are fully vaccinated.
Professor Paul Elliott of Imperial told The i: “We’re not sure why AY.4.2 might be associated with less symptomatic infection, but that might give it a transmission advantage as people carrying AY.4.2. are less likely to know that (as more of them will be asymptomatic).”
Professor Moritz Gerstung, a virologist at the University of Heidelberg, said genomic sequencing had now identified a further offshoot of AY.4.2 – called AY.4.2.1.
It accounts for between 1 and 4% of coronavirus -1>coronavirus samples in England, and may be 1% more infectious than AY.4.2.
It also does not appear to be able to escape the vaccines.