President Joe Biden’s chief medical adviser warned on Sunday that the number of Americans infected with Covid-19 was likely to “go much higher” before easing off in the new year.

Anthony Fauci told ABC News on Sunday that the “sheer volume of the number of cases . . . likely will go much higher” given the “extraordinarily contagious” nature of the Omicron coronavirus variant.

The latest figures from the Centers for Disease Control and Prevention suggested that about three-quarters of new Covid cases in the US were linked to the new variant.

“We’ve obviously got to do better,” Fauci said. “I think things will improve greatly as we get into January, but that doesn’t help us today and tomorrow.”

The US has recorded nearly 3-9m new Covid cases in the past 28 days, according to the latest data compiled by Johns Hopkins University, with a sharp rise in the past week. Many local authorities do not report coronavirus cases and hospitalization rates on weekends, but cities including New York and Washington DC have reported some of the sharpest rises in Covid cases during the holiday period.

The explosion of cases in the US mirrors trends recorded in the UK, Europe, and other parts of the world. China reported its highest rate of cases since January at the weekend, while France and Italy posted records for the number of new cases in a single day.

US comes amid a shortage of PCR and rapid at-home tests that is leading to long queues in many US cities and stoking concern that Americans have been unknowingly spreading the virus over the

they get together, especially with high-risk people . . . we have plenty of vaccine supply, that’s not a problem, but unfortunately we do not have enough tests,”

Ashish Jha, dean of the Brown University School of Public Health, told Fox