Delta-plus: is new mutation most infectious Covid-19 strain yet?

A descendent of the Delta coronavirus strain is being closely monitored by scientists who fear that the new variant may be more infectious than the original.

Experts say the AY.4.2 subvariant now accounts for almost 10% of all UK coronavirus cases and may be up to 15% more transmissible than the original Delta variant, currently the dominant strain of Covid worldwide.

Francois Balloux, director of the University College London (UCL) Genetics Institute, told the Financial Times (FT) that preliminary evidence suggested that the new Delta-plus strain may be the most infectious coronavirus variant yet in the global pandemic.

Subscribe to The Week

Escape your echo chamber. Get the facts behind the news, plus analysis from multiple perspectives.

SUBSCRIBE & SAVE

Sign up for The Week's Free Newsletters

From our morning news briefing to a weekly Good News Newsletter, get the best of The Week delivered directly to your inbox.

From our morning news briefing to a weekly Good News Newsletter, get the best of The Week delivered directly to your inbox.

Sign up

“But we have to be careful at this stage,” said Balloux. “Britain is the only country in which it has taken off in this way and I still would not rule out its growth being a chance demographic event.”

The subvariant is being monitored by the World Health Organization and could be assigned a Greek letter under the global body’s naming system if “elevated to the rank of ‘Variant under Investigation’”, he added.

Reports worldwide about the spread of the new subvariant in the UK has triggered concerns in countries including the US. The UK is seen as a “harbinger of things to come for other countries during the pandemic”, said CNBC. Some scientists have suggested that the new subvariant is a “possible factor” in the hike in case numbers in the UK over the past few months, the news site added.

On Sunday, former US Food and Drug Administration commissioner Scott Gottlieb tweeted: “We need urgent research to figure out if this delta plus is more transmissible, has partial immune evasion?”

The tally of new Covid cases in the UK reached 49,156 yesterday, the highest since 17 July. The total far outstrips those in many other European nations.

Monday’s tally is only “19,000 cases short of the peak number of cases ever recorded in the UK”, said The Guardian. The record figure of 68,053 cases was reached on 8 January, “at the height of the most devastating wave of the pandemic last winter”.

Research into the new subvariant is already under way. Jeffrey Barrett, director of the Covid-19 Genomics Initiative at the Wellcome Sanger Institute in Cambridge, told the FT that while the new variant “may make things more difficult”, the subtype “doesn’t by itself explain the recent high UK caseload”.

The subvariant contains two major spike protein mutations that “have been recorded individually in previous coronavirus lineage”, the paper reported. But why the spike protein mutations may make the AY.4.2 subvariant more infectious is unclear.

“They are not obvious candidates for immune escape, increased transmissibility or higher virulence,” said UCL expert Balloux.

Infectious disease specialist Peter Chin-Hong, from the University of California San Francisco, told the San Francisco Chronicle that the new subvariant was unlikely to be “stickier and more transmissible, make vaccines or monoclonal antibodies work less well, or cause people to become more sick”.

He explained that the two major spike protein mutations found in the new variant, A222V and Y145H, “aren’t in the place where the virus binds to the receptor”, meaning the virus is less effective at latching on to human cells.

All the same, he said, “it feels worthwhile keeping an eye on it”.