A new COVID-19 strain which is less likely to cause noticeable symptoms has been reported to be spreading throughout the United Kingdom. The AY.4.2 variant is believed to account for around 12% of the cases nationwide, in addition to being 15% more infectious than other strains known up to Nov. 5.
A report from London's Imperial College released Monday found that 66.7% of AY.4.2 cases were symptomatic, compared to 76.4% of its Delta parent, AY.4, while cases of the new sub-variant were spreading at a daily rate of 2.8%, which is why it is deemed to be between 10 to 15% more infectious than other Delta strains. At this pace, it might become the dominant type in a few months, although it may be less likely to cause symptomatic cases than previous iterations.
Symptoms such as loss or change of smell or taste, a fever, or a new persistent cough were detected in merely a third of AY.4.2 cases, against 46.3% of the AY.4 original Delta version.
The new sub-variant also doesn't seem to make vaccines any less effective, it was reported.
“It is 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,” said Christl Donnelly, professor of statistical epidemiology at Imperial College London. “It is an asymptomatic transmission that really can make the difference between what’s relatively easily containable and what needs vaccination,” he added.
Researchers have also warned it was too early to say whether the new variant is less likely to make people sick, since other factors are at play, such as more cases recorded in young people who are less likely to fall ill, or those who are fully vaccinated.
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 samples in England and may be 1% more infectious than AY.4.2.
Data from the REACT study — which measures the spread of the virus in England based on more than 100,000 swab tests — found the AY.4.2 subvariant made up 12 per cent of positive samples between October 19 and November 5.
Separate data from the UK Health Security Agency (UKHSA), which replaced the now-defunct Public Health England, showed the subvariant's weekly growth was between one and two per cent. Scientists previously predicted Covid would eventually morph into a flu-like virus that continues to spread but barely causes any deaths or severe illness.
The REACT study recorded 841 positive Covid tests during its most recent round of testing, 99 of which were the AY.4.2 sub-lineage (11.8 per cent). Its predecessor AY.4 continues to be the dominant Delta subvariant, accounting for 57.6% of all cases.