The U.S. record for daily coronavirus cases has been broken, as two highly contagious variants — Delta and Omicron — have converged to disrupt holiday travel and gatherings, deplete hospital staffs and plunge the United States into another long winter.
As a third year of the pandemic loomed, the seven-day average of U.S. cases topped 267,000 on Tuesday, according to a New York Times database. The milestone was marked after a year that has whipsawed Americans from a relaxation of rules in the spring to a Delta-driven summer wave to another surge that accelerated with astonishing speed as Omicron emerged after Thanksgiving.
The record came only a day after the Centers for Disease Control and Prevention reduced the number of days that infected Americans should remain isolated to five days from 10. The C.D.C. changed course as Omicron’s rapid spread has worsened a labor shortage, upending the hospitality, medical and travel industries, among others. The agency did not recommend rapid testing before people left isolation, and experts warned that that omission risked seeding new cases and heaping even more pressure on already overburdened health systems.
The previous U.S. daily cases record was set on Jan. 11, when the seven-day average was 251,232. That was during a catastrophic winter that was far worse than this moment, when over 62 percent of Americans are fully vaccinated. And early evidence, including some hopeful reports from South Africa, suggests that Omicron causes milder symptoms than other variants, with vaccinations and boosters helping prevent serious illness and death.
Hospitalizations have been rising, averaging more than 71,000 a day, but remain far below peak levels. While deaths have also been increasing, the daily average of 1,243 is a fraction of the record 3,342 reported on Jan. 26.
Nevertheless, Omicron has a considerably easier time than Delta infecting vaccinated people. The coming cascade of patients threatens to overwhelm hospitals just as health care workers themselves are increasingly infected.
A sizable number of patients remain infected with the deadlier Delta variant. On Tuesday, the C.D.C. reported that Omicron cases made up a significantly lower percentage of the overall U.S. caseload than was expected, at roughly 59 percent. And for the week ending Dec. 18, the agency revised down its estimate of 73 percent to about 23 percent, meaning Delta remained dominant until this week.
Omicron is undoubtedly becoming the dominant variant, and that could be good news: A new laboratory study carried out by South African scientists showed that people who had recovered from an infection with the variant might be able to fend off later infections from Delta.
Records are also being broken in Europe, but so far, the leaders of Britain, France, Spain and some other countries have resisted imposing harsh new restrictions amid calls from some who argue that it is time to accept that the virus is endemic and that countries should move away from lockdowns. These nations, confronted with Covid fatigue, are betting for now that high vaccine and booster coverage, along with earlier restrictions still in place, will be enough to keep the coronavirus manageable.
The United States has also taken a similar path, as President Biden has repeatedly said that the era of lockdowns is over and promised to increase testing, double down on vaccination campaigns and prop up hospitals. But public health experts have warned that the measures will not be sufficient to prevent soaring infections and hospitalizations over the next few weeks. And demand for tests has exploded while manufacturers are scrambling to increase production and distribution.
Testing is central to New York City’s plan to keep the largest U.S. school district open in the new year. The city announced on Tuesday that it would eliminate its policy of quarantining entire classrooms exposed to the coronavirus, and would instead use a ramped-up testing program to allow students who test negative and do not have symptoms to remain in school.
Omicron is hitting the Mid-Atlantic States especially hard. Washington, Maryland and Virginia all broke records on Monday for daily case counts.
“D.C. is a marker for what we’re likely to see in much of the rest of the country,” said Neil J. Sehgal, an assistant professor of health policy at the University of Maryland’s School of Public Health. “A tidal wave in Omicron cases is likely to flood much of the country in the next month.”