The Centers for Disease Control and
Prevention numbers showed nearly a six-fold increase in omicron’s share of
infections in only one week.
In much of the country, it’s even higher.
Omicron is responsible for an estimated 90% or more of new infections in the
New York area, the Southeast, the industrial Midwest and the Pacific Northwest.
The national rate suggests that more than 650,000 omicron infections occurred
in the U.S. last week.
Since the end of June, the delta variant
had been the main version causing U.S. infections. As recently as the end of
November, more than 99.5% of coronaviruses were delta, according to CDC data.
CDC Director Dr. Rochelle Walensky said the
new numbers reflect the kind of growth seen in other countries.
“These numbers are stark, but they’re not
surprising,” she said.
Scientists in Africa first sounded the
alarm about omicron less than a month ago and on Nov. 26 the World Health
Organization designated it as a “variant of concern.” The mutant has since
shown up in about 90 countries.
Much about the omicron variant remains
unknown, including whether it causes more or less severe illness. Early studies
suggest the vaccinated will need a booster shot for the best chance at
preventing omicron infection but even without the extra dose, vaccination still
should offer strong protection against severe illness and death.
“All of us have a date with omicron,” said
Dr. Amesh Adalja, a senior scholar at the Johns Hopkins Center for Health
Security. “If you’re going to interact with society, if you’re going to have
any type of life, omicron will be something you encounter, and the best way you
can encounter this is to be fully vaccinated.”
Adalja said he was not surprised by the CDC
data showing omicron overtaking delta in the U.S., given what was seen in South
Africa, the U.K. and Denmark. He predicted spread over the holidays, including
breakthrough infections among the vaccinated and serious complications among
the unvaccinated that could stress hospitals already burdened by delta.
Dr. Eric Topol, head of the Scripps
Research Translational Institute, said other countries had seen omicron’s fast
growth, but the U.S. data showed “a remarkable jump in such a short time.”
Topol also said it’s unclear how much
milder omicron really is compared with other variants. “That’s the big
uncertainty now.”
CDC’s estimates are based on thousands of
coronavirus specimens collected each week through university and commercial
laboratories and state and local health departments. Scientists analyze their
genetic sequences to determine which versions of the COVID-19 viruses are most
abundant.
On Monday, the CDC revised its estimate for
omicron cases for the week that ended Dec. 11, after analyzing more samples.
About 13% of the cases that week were from omicron, not the 3% previously
reported. The week before, omicron accounted for just 0.4% of cases.
CDC officials said they do not yet have
estimates of how many hospitalizations or deaths are due to omicron.
Though there remain a lot of new infections
caused by the delta variant, “I anticipate that over time that delta will be
crowded out by omicron,” Walensky said.
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