University screening programs gave scientists early insights about omicron’s spread

Omicron was first reported in South Africa on Nov. 24, 2021, and within mere days it was already making the rounds in the United States, spiking SARS-CoV-2 case numbers as it infiltrated every school, restaurant, and family gathering. But when exactly did omicron unseat the delta variant to become dominant? And how quickly did it actually take over?