Omicron has taken the hold to become the dominant Covid-19 variant in the US as more people are travelling and gathering for holidays.
The infection cases caused by Omicron amounted to 73.2 per cent of all infection cases in the week ending December 18, from 12.6 per cent of all infection cases in the week ending December 11, according to the latest model estimates of the US Centers for Disease Control and Prevention (CDC).
At the beginning of this month, Omicron only accounted for 0.7 per cent of all infection cases.
Omicron is spreading rapidly nationwide and has been found in at least 48 US states as of Monday, since the first case in the country was detected in California on December 1.
The unprecedented infectiousness of the Omicron variant and its possible ability to evade the immune system have stoked concerns across the nation. However, experts said preliminary data suggest the new variant appear to cause less severe symptoms and hospitalisations.
Covid-19 cases, deaths and hospitalizations continued to surge in the United States, leading to cancellation of large events including sports games and live concerts. Some colleges have shifted back to online classes and exams for the rest of the semester to make students go back home earlier.
The country is averaging about 130,000 new cases daily, a 10 per cent increase from the previous week, the latest CDC data showed.
The seven-day average of daily deaths is about 1,180, up 8.2 per cent from the prior week, according to the CDC weekly data.
Currently, the US is witnessing about 7,800 new hospital admissions each day, a 4.4-per cent increase from the previous week, the data showed.
New York State set Covid-19 infection record for a third straight day on Sunday with more than 22,000 positive cases. People waited in long lines at testing sites.
However, the surge in new infection cases did not deter people from flying for holidays. The US Transportation Security Administration (TSA) has screened over two million passengers for a fourth day in a row.
The TSA expected up to 21 million Americans will fly between December 23 and January 3.
Experts warned the US is moving toward Christmas in dramatically different shape than it was before Thanksgiving.
A month ago, case counts had been rising, to about 90,000 per day on average. For much of December cases appeared to hover around 120,000 but recently leaped above 130,000 per day, Johns Hopkins University data showed.
Health experts urged the public to test before heading for travels and large gatherings, getting vaccinated and boosted, masking in public indoor settings, and practicing physical distancing to slow transmissions.