The United States has hit its highest-ever average of new Covid cases as Omicron spreads at a blistering pace, amid testing woes and health worker shortages.
But the country also appears to be experiencing a decoupling between infections and severe outcomes compared to previous waves, officials noted, as evidence accumulates of milder outcomes under the new variant.
The moving seven-day average of new cases was 265,427 as of Tuesday, surpassing the previous peak of 251,989 set in mid-January 2021, a tracker maintained by Johns Hopkins University showed.
The figure is likely the tip of the iceberg, with "probably more than a half million" currently infected every day, Howard Forman, a professor at the Yale School of Public Health told AFP.
Images of people lining up to get tested, and an ongoing shortage of home kits, are becoming a political liability for President Joe Biden, who slammed his predecessor Donald Trump over mismanagement of the pandemic.
The heavily-mutated Omicron strain, which according to government modeling accounted for around 59 percent of national US cases in the week ending December 25, is the most transmissible seen to date.
It is frequently able to bypass prior immunity conferred by vaccination and prior infection.
Omicron is already stretching previously strained hospital systems throughout the country, with health workers leaving in droves because of burnout.
Hospital systems are turning to "travel nurses" on lucrative short term contracts to overcome shortages.
While the trend is worrying, the hospitalizations and deaths "remain comparatively low right now," Centers for Disease Control and Prevention (CDC) director Rochelle Walensky told reporters on a call.
"This could be due to the fact that hospitalizations tend to lag behind cases by about two weeks, but may also be due to early indications that we've seen from other countries like South Africa and the United Kingdom have milder disease from Omicron," she added.
Nationwide, around 9,000 Covid patients are being admitted every day, while 1,100 are dying.
- Concern but also hope -
Biden's top medical advisor Anthony Fauci underscored that the "spike in cases is out of proportion to the increase in hospitalization" and that, based on the totality of global research, "all indications point to a lesser severity of Omicron versus Delta."
It is still difficult to gauge to what extent better outcomes under Omicron are due to prior immunity from past infections or vaccination, versus intrinsic properties of the virus.
Animal and lab data indicate Omicron is less effective at spreading in the lungs, Fauci added.
Experts are hoping that the country's experience will be more like a "flash flood" as seen in South Africa, where it was first reported in mid-November but where cases have been receding since more than a week.
In Britain, where cases have also skyrocketed, new Covid deaths have so far remained flat.
Forman told AFP that northeastern US states still battling Delta were faring worse than places such as Florida, where the primary strain is Omicron.
More than 820,000 Americans have died from Covid, making the United States by far the hardest-hit country in the world, ahead of Brazil and of India.
By October, the latest month for which data has been analyzed, unvaccinated people had a five times greater chance of being infected with Covid, and 14 times higher chance of dying, compared to vaccinated people.
Though that data does not account for Omicron, early research shows vaccination and boosting continue to protect well against severe outcomes.