- Delta subvariant AY.4.2 observed in June by the Sanger Institute in the UK, which sequences Covid samples
- Its prevalence has doubled in a month from 4 percent in September to 9 percent in October, its data shows
- Experts estimate that it may be 15 percent more contagious than Delta, which is the dominant worldwide
- Number 10 said it ‘won’t hesitate to take action if necessary’, but warned that there is no evidence it spreads more easily
- It comes amid rising cases in the UK, which have reached a three-month high of nearly 50,000
A subtype of the Covid delta strain may be more contagious than its ancestor, experts warned today after data showed the proportion of cases linked to the strain doubled in a month.
AY.4.2, as it is currently known to scientists, made up about 10 per cent of all infections in England in the fortnight ending 9 October. Virus-trackers at the Wellcome Sanger Institute, which sequences thousands of Covid samples every week, say the spread was only four per cent in mid-September.
Academics estimate that it could be up to 15 percent more permeable than the original Delta, which became increasingly effective in Britain in the spring before flying around the world.
It has been detected in almost every part of the country, statistics show, and it is believed to be behind nearly 60 percent of positive tests sampled in Adoor, West Sussex.
No10 said today that it is keeping a ‘very close eye’ on AY.4.2, but stressed that there is ‘no evidence’ that it spreads easily. Boris Johnson’s official spokesman also warned the government “will not hesitate to take action if necessary”.
The warning comes as Covid cases continue to rise across the UK, with daily infections reaching a three-month high yesterday of nearly 50,000.
Experts suggested an increase of AY.4.2 – one of Delta’s 45 subpopulations – may be partly to blame, along with the return of pupils to classes and workers’ offices since August.
SAGE fears that by the end of the year there will be a fourth wave that could cripple the NHS. The minister is overseeing the rollout of booster jabs for people over the age of 50, healthcare workers and the immunosuppressed, to protect healthcare as much as possible.
But experts warn that top-up jabs are being phased out too slowly, with 5 million vulnerable adults yet to be eligible for a third dose.
Influential government advisor Professor Neil Ferguson, an epidemiologist at Imperial College London, stressed today that it is ‘important we accelerate’ the booster drive to give ourselves the best chance of avoiding rolling back restrictions.
The graph shows the proportion of cases sequenced in England that are the new subtypes AY.4.2 (yellow) and delta (blue). Delta becomes dominant in the UK in May, overtaking the previously dominant alpha strain (purple)
The map shows the proportion of cases caused by AY.4.2 from the fortnight to October 9, with darker colors equating to more infections caused by the subvariant. Data from the Sanger Institute shows that 8.9 percent of all Covid-positive nose and throat inflammations indexed in England were caused by AY.4.2. These data suggest that the sub-lineage is most prevalent in Adoor, where 61 percent of all positive samples sequenced were associated with AY.4.2. The subtype also appears to be highly prevalent in East Lindsay (46 percent) and Torridge (41 percent).
The spread of the Delta strain, which was first detected in the UK in March and took effect within two months, has increased much faster than in AY.4.2. Delta still accounts for nine out of 10 infections in England
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