Omicron’s arrival in November 2021 took scientists by surprise. Not because there was a new variant on the block, but because it had many unusual mutations—some rare and others that had never been seen before. Also, its closest relatives weren’t recent variants but earlier versions of SARS-CoV-2, the virus that causes COVID-19, circulating more than a year ago.
That left the scientific community wondering where, exactly, Omicron came from. Some research suggests that this variant may have evolved in the body of someone who was immunocompromised; other molecular clues suggest that the virus jumped from a human to an animal where it evolved before jumping back into a human host.
But there’s another hypothesis that has gained attention: Perhaps Omicron simply evolved in a relatively isolated region that had limited capacity to analyze the genetic sequences of COVID-19 virus samples. That means Omicron could have circulated undetected in a population for a long time.
For instance, the B.1.620 variant of interest was first detected in Lithuania in April 2021, but researchers traced back its origin to central Africa, where some countries have grappled with limited genomic surveillance capabilities.
