New York state reported Friday that just over 21,000 people had tested positive for COVID-19 the previous day, the highest single-day total for new cases since testing for the virus became widely available.

One day snapshots of virus statistics can be an unreliable way to measure trends, but the new record punctuated a steady increase that started in the western part of the state in late October, and has taken off in New York City in the past week.

Just under half of the positive results were in the city, where lines were growing at testing stations and some Broadway shows and the Rockettes Christmas show were cancelling performances because of outbreaks among cast members.

The steep rise in infections should be of great concern but it was inevitable, given the quick spread of the omicron variant, said Dr. Denis Nash, the executive director of the Institute for Implementation Science in Population Health at the City University of New York.

“We were already headed for a winter surge with delta, which is a very concerning thing in its own right,” Nash said.

“But then you layer on top of that the new omicron variant, which is more transmissible from an infection standpoint,” he said, noting that current vaccines may be unable to contain the “more invasive” new variant.

Nearly 10,300 of the positive tests reported by the state were in the city, roughly comparable to its share of the state's population.

Statewide, New York averaged 13,257 positive tests per day over the seven-day period that ended Thursday. That is up 71% from two weeks ago.

The state's previous one-day high for positive tests came on Jan. 14, 2021, when just under 20,000 people tested positive.

"I can confirm this is the most positive tests reported in a single day, but important to remember we did not have this access to testing in the first wave. So comparing these numbers to March/April 2020 would paint an incomplete picture," said a Department of Health spokesperson.