Omicron’s Explosive Growth Is a Warning Sign

A lot is still unknown around Omicron, but a worrying trend has become clear: This variant sure is spreading fast. In South Africa, the U.K., and Denmark—countries with the best variant surveillance and high immunity against COVID—Omicron cases are growing exponentially. The variant has outcompeted the already highly transmissible Delta in South Africa and may soon do the same elsewhere. According to preliminary estimates, every person with Omicron is infecting 3–3.5 others, which is roughly on par with how fast the coronavirus spread when it first went global in early 2020.

In other words, Omicron is spreading in highly immune populations as quickly as the original virus did in populations with no immunity at all. If this holds and is left uncontrolled, a big Omicron wave lies ahead—bigger than we would have expected with Delta. Cases were already surging ahead of winter. The U.S. already had a too-low vaccination rate. And now Omicron threatens to eat away at the