Illustration of the Omicron variant of SARS-CoV-2 (orange), the cause of Covid-19. The highly transmissible Omicron variant of SARS-CoV-2, BA.1, accounted for nearly all of the coronavirus infections globally in early 2022. Numbers of Omicron infections can double in under two days, which is significantly faster than previous SARS-CoV-2 variants and closer to what public-health officials would expect from the influenza virus.