With the news that South Africa has passed the peak of its coronavirus cases caused by the omicron variant, scientists are projecting that the United States’ sharp increase in cases will crest as soon as the middle of January.

Over the past month, the omicron variant has spread around the world with astonishing speed, even among people who are vaccinated or who had recovered from previous infections. On Thursday, the United States surpassed 580,000 cases, beating the record set only a day before.

That is believed to be a vast undercount, because of testing shortages, the popularity of at-home tests and reporting delays over the holidays. What’s more, a significant number of people may have asymptomatic infections and never know it.

New estimates from researchers at Columbia University suggest that the United States could peak by Jan. 9 at around 2.5 million cases per week, although that number may go as high as 5.4 million. In New York City, the first U.S. metropolis to see a major surge, the researchers estimated that cases would peak by the first week of the new year.

“It’s shocking. It’s disturbing,” said Jeffrey Shaman, a public health researcher who led the Columbia modeling work. “We’re seeing unprecedented numbers of COVID-19 cases.”

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The variant is significantly milder than delta and other versions of the virus and is far less likely to lead to hospitalizations, according to data from South Africa and preliminary data from Britain released Friday.

Still, the enormous numbers of people getting simultaneously infected could greatly strain hospitals, experts said, especially in places with lower vaccination rates or in places where hospitals are already overburdened. Just how much of a burden the variant will be, however, depends on how quickly it will burn out in particular communities, especially in large cities.

Those complex transmission dynamics have been maddeningly difficult to predict with precision.

Another model, released by a research group from the University of Washington last week, estimated that the United States would reach a peak in cases by the end of January. But even those researchers are now rethinking their projections based on omicron’s rapid spread.

“We are realizing right now monitoring the data that the peak is going to come much faster,” said Ali Mokdad, a public health researcher at the University of Washington. “My guess is it will happen before mid-January.”

The numbers are increasing so quickly that some public health researchers say modeling isn’t even necessary to see where things are headed, said William Hanage, a public health researcher at the Harvard T.H. Chan School of Public Health.


“The context for all of this is that hospitals are struggling,” Hanage said. “We don’t have that much spare capacity. And of course, omicron makes that worse.”

There are some reasons to think that the variant’s behavior in the United States might be different than in other countries. In South Africa, for example, the population is much younger, and a large proportion had been infected by earlier waves of the virus. In Britain, the vaccination rate for older people is much higher than in the United States.

While South Africa saw a rapid increase in cases followed by a sharp decline, it’s unclear whether cases will crest in the United States in a similar fashion. Because of the number of unknowns, including the emergence of new variants and government restrictions aimed at curbing transmission, Shaman’s group limits its projections to four to six weeks in the future.

Two things can cause new infections to decline, according to Natalie Dean, a public health researcher at Emory University. The biggest contributor is that the virus can burn through people in certain communities, especially dense cities; when it stops finding people to infect, new cases decline. People may also change their behaviors, whether through societal restrictions or on their own, giving the virus fewer opportunities to find them.

“Our communities are complicated — it doesn’t mean that everyone in the community has gotten infected,” Dean said. “It’s kind of the people who are most connected.”

The United States could also see more localized outbreaks, with cases beginning to decline in current hot spots, like New York City and Washington D.C., just as they’re beginning to take off elsewhere. That could lead to more of a rounded peak instead of a sharp turnaround, Shaman said.