Scientists predict omicron will peak in the US in mid-January but still may overwhelm hospitals

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 US 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.”

The variant
is significantly milder than delta and other versions of the virus and is far less
likely to lead to hospitalisations, 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
realising 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. “You don’t even need a
model for this,” said William Hanage, a public health researcher at the Harvard
TH Chan School of Public Health.

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.

And although
omicron causes milder illness than previous variants, surging cases could send
more people to the hospital. “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.”

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 localised outbreaks, with cases beginning to decline
in current hot spots, like New York City and Washington DC, 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.

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