New York officials reported 21,027 new coronavirus cases on Friday, the highest single-day total since the earliest days of pandemic, when the availability of testing was not as widespread as it is now.
The data, which reflected test results for Thursday, showed a drastic change in the virus’s presence in New York. For weeks, case counts had been rising steadily, primarily because of a winter surge driven by the Delta variant. But the spike in recent days is because of the fast-spreading Omicron variant, epidemiologists believe.
Dr. Wafaa El-Sadr, an epidemiology professor at Columbia University, said that for now, the Omicron variant seemed to be infecting more people in New York than in other parts of the country.
“In that sense, this sort of reminds me of March 2020,” she said. “We are taking the first wave of Omicron in this country, and, similar to the last time in New York, we will be essentially the testing ground for what this variant will do.”
Virus cases in the state have risen 56 percent in the past 14 days, and hospitalizations, though far below the peaks of the past two years, have climbed 25 percent in the same period, according to The New York Times’s tracker. As of Thursday, the state’s positivity rate had climbed to nearly 8 percent.
The surge in cases, Gov. Kathy Hochul said on Friday, “is a reminder that the pandemic is not over yet and we must take extra care to keep ourselves and each other safe.”
Earlier this week, in an effort to curb the virus’s spread — especially with the winter and holiday season at hand and many people planning to travel and spend more time indoors — Ms. Hochul imposed a statewide mandate requiring that masks be worn at all indoor public spaces that do not require proof of full vaccination against the virus for entry.
In one high-profile sign of the surge’s impact on New York City life, the producers of Radio City Music Hall’s enduring Christmas show starring the Rockettes said late Friday that they would end this season’s run entirely over “increasing challenges from the pandemic.”
The announcement followed canceled performances by a number of Broadway shows and decisions by some New York colleges to cancel some activities or conduct final exams remotely.
In another effort to contain the virus’s spread, Ms. Hochul has also said that state officials planned to change the definition of fully vaccinated to include receiving a booster dose.
“People who are certainly eligible, we want them to do it, but, in terms of requirement, we just have to make sure that we adapt to that flexibility required, but we’ll get it done,” the governor said in an interview on CNN. She noted that people who had recently been vaccinated were not yet eligible to receive booster shots.
In New York City in recent days, case counts have doubled from a week ago.
“This big jump, that only happens when something big changes and the only big thing that has changed citywide is Omicron,” said Dr. Denis Nash, an epidemiology professor at the CUNY School of Public Health. However, there is little reliable, up-to-date data indicating what percentage of the new cases in the city are being caused by the variant.
Mayor Bill de Blasio has encouraged New Yorkers to get booster shots expeditiously.
“People need to get vaccinated right now, get that booster right now,” he said on Thursday. “If they are not feeling well, get tested right now. It’s an urgent situation.”
On Thursday, the mayor announced a plan to confront the surge in cases by, among other plans, distributing a million free KN95 masks and 500,000 at-home tests, enforcing mask and vaccine mandates more rigorously and expanding hours and capacity at city-run testing sites.
Many New Yorkers have been rushing lately to get at-home testing kits, with some stores selling out, and the lines of people waiting at some testing sites have wrapped around blocks. The Omicron variant has been tearing across New York, including among vaccinated people.
“Two of my friends who are vaccinated — one who was boosted — got Covid just this past week,” said Gene Goldstein-Plesser, 32, as he waited to get tested at a city-run site in the Fort Greene section of Brooklyn on Thursday. “I literally just got an email that a party I was going to go to this weekend is canceled.”
Mr. Goldstein-Plesser said the hardest part about the surge was “going back into that horrible math around, like, where are you willing to take risks? And where are you not willing to take risks in your own life?”
The single-day case count announced on Friday may not be the highest of the pandemic because a number of virus cases went unreported early on when the testing infrastructure was not fully in place. But it is still clear that cases have risen significantly in the state.
The Omicron variant appears to be spreading quickly among vaccinated people and unvaccinated people alike. Nowhere is that clearer than at Cornell University, in Ithaca, where 99 percent of students who are on campus have been inoculated against the virus.
Still, case counts among the student body skyrocketed this week. There were 1,567 student cases in the seven-day period that ended on Thursday, out of more than 26,000 students. The positivity rate was above 7 percent.
Only a fraction of positive cases are analyzed to determine whether they are Delta, Omicron or another variant. But in Tompkins County, which includes Ithaca, about 117 Omicron cases have been detected, more than in any other county, according to the governor’s office.
Cornell officials moved the campus to “Alert Level Red” for the first time in the past three semesters after a surge in cases, introducing a number of safety measures that included moving final exams online and canceling a December graduation. New York University, also facing a surge, canceled “nonessential” gatherings this week.
Matt Stevens contributed reporting.