What to Know About XBB and Other Omicron Subvariants

Since emerging in late 2021, the highly transmissible omicron strain of SARS-CoV-2 has splintered into an expansive array of subvariants that are driving new waves of Covid-19 around the world. The proliferation of such a diversity of variants is unprecedented and pits numerous hyper-mutated iterations against each other in a race for dominance. That’s turbo-charged Covid, making it one of the fastest-spreading diseases known to humanity and further challenging pandemic-mitigation efforts in a global population that has largely abandoned booster shots, testing and masking.

Omicron was first identified in southern Africa in late 2021, when it outcompeted the delta variant. Its initial iteration, B.1.1.529, is characterized by some 30 mutations in the gene for the spike protein, which gives the coronavirus its crown-like appearance and allows it to invade cells. Changes there can make the pathogen less recognizable to the antibodies the immune system makes in response to vaccination or a case of Covid, increasing the risk of infection.