PARIS - The US, Britain, France and Australia have all announced record numbers of daily Covid-19 cases as the WHO warned Tuesday that Omicron's dizzying spread increased the risk of newer, more dangerous variants emerging.

Britain breached 200,000 cases for the first time on Tuesday, Australia posted almost 50,000 and France registered more than 270,000, all three countries easily topping their previous records.

But dwarfing even those numbers was the 1,080,211 reported by the United States on Monday, a global record.

The country's Monday figures are usually higher due to delays in weekend tallying -- and were likely inflated further after a three-day New Year's holiday weekend.

The rolling average over seven days -- which experts see as more reliable -- was 486,000 cases per day as of Monday evening, Johns Hopkins University said.

The heavily mutated Omicron variant, the most transmissible to date, accounted for around 59 percent of US cases near the end of last year.

Omicron's rates of deaths and hospitalisations have been lower across the world, raising hopes the virus could be evolving into a relatively benign seasonal illness.

But the World Health Organization in Europe sounded an ominous note of caution on Tuesday, warning the soaring infection rates could have the opposite effect.

"The more Omicron spreads, the more it transmits and the more it replicates, the more likely it is to throw out a new variant," WHO senior emergencies officer Catherine Smallwood told AFP in an interview.

"Now, Omicron is lethal, it can cause death... maybe a little bit less than Delta, but who's to say what the next variant might throw out," she added.

"Even in well-capacitated, sophisticated health systems there are real struggles that are happening at the moment."

AFP