How worried should we be about the "delta plus" variant?

The variant is spreading across the UK – so Salon spoke to experts about whether the US could be next

By Nicole Karlis

Senior Writer

Published October 27, 2021 3:00PM (EDT)

Coronavirus mutations, concept (Getty images/VICTOR HABBICK VISIONS/SCIENCE PHOTO LIBRARY)
Coronavirus mutations, concept (Getty images/VICTOR HABBICK VISIONS/SCIENCE PHOTO LIBRARY)

The delta subvariant known as AY.4.2 – ominously dubbed "delta plus" – is TKing headlines as cases of it are increasing in the United Kingdom.

Earlier this month, the U.K.'s Health Security Agency published a report stating "a delta sublineage newly designated as AY.4.2 is noted to be expanding in England." The descendant of the highly transmissible delta variant has two mutations to the spike protein, and it appears to be on "an increasing trajectory" as most recent data suggests it made up approximately 6% of all sequenced cases in the U.K. 

So what does this mean for the United States?

First of all, the delta subtype variant has already been detected on our shores. However, the Centers for Disease Control and Prevention (CDC) has recently stated delta plus is not a cause for concern . . . yet, but the agency is monitoring the situation closely.

READ MORE: Delta variant twice as likely to hospitalize victims, new study finds

"We're watching it very carefully," CDC Director Rochelle Walensk Walensky said on NBC's Meet the Press last week. "We have had a handful of cases here in the United States, but it has not taken off as it has in the U.K."

As some may recall, before the delta variant exploded in the U.S., it was the dominant strain in the United Kingdom. In many ways countries in the U.K. have become blueprints for the United States, which is why news about the "delta plus" variant increasing abroad can be unnerving for Americans. Does this mean a delta-plus wave is imminent?

Experts who have been following the pandemic tell Salon it's likely not going to be worse than the original delta surge, but it is a variant to keep track of since it's possible that AY.4.2 is more transmissible than the current dominant delta variant.

"Any variant is potentially a cause for concern, and given what happened with delta I'd be really hesitant to say something absolutely isn't a problem, particularly given how little we know," Justin Lessler, a professor in the Department of Epidemiology at the University of North Carolina's Gillings School of Global Public Health, told Salon. "But that being said, what we do know about the delta plus variant doesn't indicate to me that it's a major problem, at least for the United States.

"It looks to be about 10% more transmissible than delta," he continued, "and in our work on the scenario modeling hub, when we looked at a hypothetical variant that was 50% more transmissible than delta, we did see resurgences in that case, but we didn't see big ones that put us back to the size of the delta wave or last winter's winter wave."

Want more health and science stories in your inbox? Subscribe to Salon's weekly newsletter The Vulgar Scientist.

Indeed, Lessler is part of the COVID-19 Scenario Modeling Hub Coordination Team which has modeled a series of projections based on different scenarios; one being a more transmissible delta variant emerging. But as Lessler noted, the "delta plus" variant in question is estimated to be only 10% more transmissible, which many believe isn't enough to cause another major wave.

Monica Gandhi, infectious disease doctor and professor of medicine at the University of California–San Francisco, told Salon the delta variant will mutate. That's to be expected, but the only reason all eyes are on  AY.4.2 is because it does appear to be slightly more transmissible.

"The thing about the delta variant is we've seen other variants come and go, like mu and lambda, and this is the only one that we're watching just because it could be more transmissible, none of the other ones were more transmissible," Gandhi said. "So I think it's the right thing to do, to watch, but I will tell you that there's simply no evidence that it beats the vaccines, which is, of course, the scariest thing that could ever happen from a variant."

Gandhi said, delta plus can hypothetically still infect people who had the delta variant or have been vaccinated, but there's no evidence that the symptoms it causes will be more severe.

"It can definitely go into your nose, but that doesn't mean you get more sick from it," Gandhi said. "If it's more visible, like 10%, it can go in your nose, you can detect it, you can have an asymptomatic infection, but if we haven't seen that people get more sick from it."

Gandhi added the U.S. is better positioned to deal with a delta surge today than it was in early July when the delta variant took off here because now more people are vaccinated. Gandhi pointed to a modeling study published in the Annals of Internal Medicine estimating that the population immunity in the U.S. was estimated to be at 62% in early July prior to the delta surge. Today, that percentage is higher.

"With 34 million new shots and likely more than 30 million new infections, we could be up to over 85% seroprevalence now," Gandhi said in a follow-up email to Salon. "With over 80% or even 90% to achieve control against delta, we may be approaching this level now."

Since the delta variant seeks out unvaccinated individuals, there will be fewer people for a subtype variant like delta plus to infect.

What scientists do know about this variant is that it has two mutations to the spike protein, which can better assist it in invading its host's cells. Still, many uncertainties about delta plus remain.

"These are the mutations that have been flagged by the researchers as potentially interesting mutations to observe, but what role they do play in terms of the kind of how AY.4.2 behaves remains to be seen," said Sasan Amini, founder and CEO of Clear Labs, a private genomics company. "It remains to be seen what these mutations actually do."

Amini added that it's notable that  AY.4.2 was first identified in the United Kingdom in April 2020, as confirmed by data from

"And it isn't a dominant variant yet, compared to the delta one, but it has been growing," Amini said. "Part of that more rapid growth could be attributed to some of the mutations that  AY.4.2 has actually accumulated over time, and so we should always factor those specific evolutionary times into the configuration, so certainly the track record of the variant in the U.K. makes it interesting for us to to observe, but it's too early to say that this is going to turn into a key variant of concern for us."

Other stories you may like: 

By Nicole Karlis

Nicole Karlis is a senior writer at Salon, specializing in health and science. Tweet her @nicolekarlis.

MORE FROM Nicole Karlis

Related Topics ------------------------------------------

Ay.4.2 Delta Plus Pandemic Reporting Variant