FAMILY EMERGENCY — The BA.2.12.1 Covid subvariant of BA.2, a subvariant of SARS-CoV-2 variant Omicron, is taking hold in the U.S. If you're confused by the above sentence, you're not alone. It's been hard enough to keep track of all the new variants of the coronavirus, from Alpha to Delta to Omicron. Now this year has seemed to bring on a new term for our brains to digest: subvariants. Even experts are a touch confused. One scientist joked with Nightly that he was having "trouble" with the long list of subvariant numerals, which begin to sound like a "bloody phone number." Another, who wasn't near a computer when we talked, said to check his numbers as he tried to list the "2.12.1" off the top of his head. When and why did we start talking about subvariants? What is a subvariant, what makes it different from a variant, and who the heck decides which is which? "What we call a new variant, or subvariant, is to some degree, arbitrary," Jesse Bloom, a virologist at the Fred Hutchinson Cancer Research Center who studies the evolution of viruses, told Nightly. But it's not totally made up, either. BA.2 and others have been named subvariants because they share important mutations that place them under the Omicron family tree, Bloom said. Before we go further, let's take a look at this family tree: — BA.1 was what we called the original Omicron. — Soon after the discovery of BA.1, scientists identified BA.2 and BA.3. Bloom calls these "sister" lineages. Scientists know they're "sisters" because they share common mutations but each have their own distinct mutations as well, which tells researchers that one wasn't descended directly from the other. They're each descendants of the original virus, SARS-CoV-2. — BA.3 failed to effectively transmit, but the fitter sister, BA.2, began to spur outbreaks in the U.S. this spring. — Then BA.2 went off and had kids of its own: It's now evolved its own subvariant, BA.2.12.1, which appears to be even more transmissible and is leading to a rise in cases across the U.S. — In South Africa, scientists have identified BA.4 and BA.5, which by the names would lead you to think they're also "sister" lineages descended from the original SARS-CoV-2. But with further study, Bloom said, scientists think it's possible these, too, could be descendents of BA.2, just like BA.2.12.1. Weekly cases have tripled in the region over the last two weeks. So it makes sense that you're confused. Why are these considered subvariants instead of new variants that get a new Greek letter? There's no hard-and-fast rule. It's a judgment call. "To a large degree, when WHO/CDC choose to name them as such," William Hanage, an epidemiologist at Harvard T.H. Chan School of Public Health, told Nightly. We'll likely continue to call these Omicron offshoots "subvariants," Hanage said, because the CDC and WHO decided to use the terminology for BA.2, even though it has "clinically significant mutations" that help it escape antibodies from vaccines and prior infection. BA.2 maybe should have been the Pi variant. And maybe one day BA.2 will graduate to variant status, Bloom said, if Omicron continues to perform as well as it has, overtaking other variants of Covid. If all the SARS-CoV-2 viruses become relatives of Omicron, experts might shift to using "variants" for the Omicron subvariants. No matter what we call it, the virus will continue its natural evolution, and we should expect the seasonality of Covid to play out in the U.S. as it did in 2020 and 2021, Hanage said. He'll be closely watching states like Texas and Florida, to see if cases of BA.4 and BA.5 tick up throughout the summer months. "The next real crunch point — and this is even incorporating BA.4 and BA.5 — is probably going to be when we turn into the fall and winter," he said. "People who were infected with BA.1, and BA.2, will be susceptible to infection again," both from the continual evolving of the virus and the waning of immunity from vaccines and prior infections. Scientists are trying to figure out exactly where these variants came from in the first place, Hanage said. Preliminary evidence suggests at least some emerged from long-term Covid infections in immunocompromised patients. There's a growing school of thought that BA.1 and BA.2, Hanage said, might have formed in the same person. "In such cases, the virus can accumulate large amounts of variation and explore evolutionary space to get better at infecting cells and sidestepping the immune system," Hanage said. "This is one of the reasons that it is really important to make sure such folks get the best possible treatment, including access to appropriate drugs like Paxlovid or Evusheld." Welcome to POLITICO Nightly. Reach out with news, tips and ideas at nightly@politico.com. Or contact tonight's author at mward@politico.com, or on Twitter at @MyahWard.
| 
Comments
Post a Comment