The U.S. is facing an imminent COVID-19 "viral blizzard," infectious disease expert Michael Osterholm told CNN Thursday.

What they're saying: "In the next three to eight weeks, we're going to see millions of Americans are going to be infected with this virus, and that will be overlaid on top of Delta," said Osterholm, the director of the Center for Infectious Disease Research and Policy at the University of Minnesota.

The latest:

• Omicron study: Vaccines produced by Johnson & Johnson and China's Sinopharm, as well as the Russian-made Sputnik V, provided little or no protection against the Omicron variant in a new study.
• Biden's warning: President Biden warned unvaccinated Americans that the Omicron variant will start to spread more rapidly in the U.S. if they do not receive their shots soon.
• Health care's breaking point: New waves of infections are crashing into a health care system whose workers are at a breaking point — if not already past it.
• NYC on alert: New York City — America's original pandemic epicenter — is displaying warning signs of yet another drastic surge of the virus, this time likely driven by the Omicron variant.
• Grip tightens on sports world: COVID continues to rip through professional sports at an alarming rate, prompting leagues around the world to update protocols, limit fan capacity, postpone games and consider temporary shutdowns.
• Reinfection risk: A new study shows that having had COVID-19 offers little protection against the Omicron variant, Bloomberg reports.
• Omicron dashboard