That this competition is blatantly favoring Omicron so far does not necessarily tell us where Delta will end up. All infections are interactions between pathogen and host, which means Delta could hold its own, or make a comeback, for a bunch of reasons that aren’t just about the virus itself. Some people could, for instance, be more biologically primed to foster a Delta infection than an Omicron one. Or Delta could exploit the vagaries of geography, taking stubborn root in an isolated population without much immunity of any kind, in which case Omicron’s advantage may be moot. Or it could find shelter in a little community where few Omicron-infected people have yet to tread—or, perhaps more concerningly, in an immunocompromised person, infected months ago, who has so far struggled to purge the virus.

Variants in this way are like pickles: They have a way of sticking around past their anticipated expiration date. Even Alpha (remember Alpha?) still occasionally blips back onto the map, though recorded instances remain quite rare. These cases can be hard to catch; researchers don’t have the capacity to detect, let alone sequence, every SARS-CoV-2 infection out there. That means the proportions of variants in the genomes researchers report aren’t necessarily representative of their proportions in the wild. “The world is a very big place, and it’s all a numbers game,” Benhur Lee, a virologist at Mount Sinai’s Icahn School of Medicine, told me.

And the longer Delta is able to bide its time, the more easily it might be able to engineer its own revival.