Ever since delta tore away illusions that this pandemic thing was on the run, there has been a concern over other potential variants that might create the next big jump in cases. The World Health Organization jangled nerves when it added lambda and mu to its list of “variants of interest,” but while both of those variants had features that could potentially increase the chance of a bad outcome from infection, neither proved to be as easily transmissible as delta. Both variants are now essentially “extinct” in the U.S. after making small inroads. They simply couldn’t compete with the big D.

Case counts in the United States remain high relative to most of 2020, and much higher than they were in the spring, when it seemed that a return to “normal” was tantalizingly close. Still, the slow decline of cases in the U.S. matches the predictions made in September by the merged results of the COVID-19 Scenario Modeling Hub.  Despite a delta variant level that is now essentially 100% of U.S. cases, continued masking in major cities, along with a slowly increasing level of vaccination (now at 66.1% of the total population, or 77.3% of those over 12, according to the Centers for Disease Control and Prevention) have cut cases to half of where they were in August. 

If childhood vaccinations begin in the next few weeks, and follow the same trends as vaccinations among adults, cases are expected to drop to one quarter of current levels by the end of the year.

But the pattern in the U.K. is very different. Cases dropped about 40% from the peak, then began staggering back up. In the last two weeks, case counts have increased at a pace that nearly matches that of June and July. In fact, there have been more confirmed cases in the U.K. since June than there were in the whole of the pandemic before that date.

But if the analysis from U.K. virologists Jeffrey Barrett and Francois Balloux is correct, the AY.4.2 subvariant may have the one thing that mu and lambda lacked: a higher rate of transmission than delta. In fact, this may be the most transmissible form of the SARS-CoV-2 virus seen so far. 

As the name implies, the AY.4.2 subvariant doesn’t diverge far from the original delta. Which makes it one of several subvariants that have also been tagged “delta plus.” It’s thought to be between 10% and 15% more transmissible than “standard” delta, though it’s not clear why. Delta’s big edge over other variants appears to be simply that it produces far more virus in the respiratory tract where it can easily be spread. AY.4.2 could be doing the same thing, only moreso.

Right now, the U.K. is the only country known to have a significant level of AY.4.2, with the subvariant accounting for about 10% of confirmed cases. Researchers warn that the “more contagious than delta” description could turn out to be false. When looking at just one country, and just a fraction of that country, other factors may have driven AY.4.2 to temporary prominence. After all, lambda and mu seemed to be growing at one point before being lost in the delta sea. It will take time to see if AY.4.2 really is “delta+.”

However, even if the new subvariant is as contagious as researchers believe, that’s not enough of an improvement over delta to account for the way U.K. cases continue to rise. A 10% or even 15% increase also isn’t enough to change the projection for the U.S., should that variant spread outside the U.K. The delta variant was more like two times as contagious as the alpha variant, which was itself about twice as contagious as the original “wild type.” It’s not A.Y.4.2 that’s keeping counts up in the U.K., and it shouldn’t cause lost sleep in the U.S. 

The answer there isn’t any change in the virus. It’s a change in the people.

Coronavirus is more prevalent in Britain mainly because of reduced emphasis on measures such as mask-wearing, social distancing, ventilation, and working from home …

It’s that last part that should be a concern to everyone. Genuinely ending the pandemic is going to require persistent use of masking and social distancing measures, in addition to expanded use of vaccination. Letting down our guard is a bigger threat than any new variant.