Why Hasn’t the U.S. Found More Omicron Cases?

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Genomic surveillance has improved enormously successful caller months, but the strategy has built-in delays, and unsighted spots remain.

Analyzing a Covid trial  illustration   successful  a laboratory  successful  Houston. The state  is present  sequencing astir    80,000 microorganism  samples a week and 14 percent of each  affirmative  P.C.R. tests, but the process   is time-consuming.
Credit...Brandon Bell/Getty Images

Dec. 2, 2021, 2:17 p.m. ET

Last Friday, conscionable a time aft South African scientists archetypal announced the find of the Omicron variant, Europe reported its archetypal case: The caller coronavirus variant was successful Belgium. Before the play was out, Australia, Britain, Canada, Denmark, Germany, Israel, Italy and different countries had each recovered cases.

But successful the United States, scientists kept searching.

“If we commencement seeing a variant popping up successful aggregate countries crossed the world, usually my intuition is that it’s already here,” said Taj Azarian, a genomic epidemiologist astatine the University of Central Florida.

On Wednesday, American officials announced that scientists had recovered it — successful a California diligent who had precocious returned from South Africa. By then, Canada had already identified six cases; Britain had recovered more than a dozen.

The United States identified a 2nd case, successful Minnesota, connected Thursday, and much are astir surely lurking, scientists said. So wherefore haven’t we recovered Tthem yet?

Multiple factors whitethorn beryllium astatine play, including question patterns and stringent entranceway requirements that whitethorn person delayed the variant’s instauration to the United States. But unsighted spots and delays successful the country’s genomic surveillance strategy whitethorn person been factors, too, experts said. With galore labs present conducting a targeted hunt for the variant, the gait of detection could rapidly prime up.


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Since the opening of the pandemic, scientists person been sequencing the familial worldly from samples of the virus, a process that allows them to spot caller mutations and place circumstantial variants. When done routinely and connected a ample scale, sequencing besides allows researchers and officials to support tabs connected however the microorganism is evolving and spreading.

In the United States, this benignant of wide genomic surveillance got disconnected to a precise dilatory start. While Britain rapidly harnessed its nationalist wellness attraction strategy to motorboat an intensive sequencing program, aboriginal sequencing efforts successful the United States, based chiefly retired of assemblage laboratories, were much constricted and advertisement hoc.

Even aft the C.D.C. launched a sequencing consortium successful May 2020, sequencing efforts were stymied by a fragmented wellness attraction system, a deficiency of backing and different challenges.

In January, erstwhile cases were surging, the United States was sequencing less than 3,000 samples a week, according to the C.D.C.’s dashboard, acold little than 1 percent of reported cases. (Experts urge sequencing astatine slightest 5 percent of cases.)

But successful caller months, the concern has improved dramatically, acknowledgment to a operation of caller national leadership, an infusion of funding and an expanding interest astir the emergence and dispersed of caller variants, experts said.

“Genomic surveillance truly has caught up successful the U.S., and it is precise good,” said Dana Crawford, a familial epidemiologist astatine Case Western Reserve University.

The state is now sequencing astir 80,000 microorganism samples a week and 14 percent of each affirmative P.C.R. tests, Dr. Rochelle P. Walensky, the manager of the Centers for Disease Control and Prevention, said astatine a White House briefing connected Tuesday.

The occupation is that the process takes time, particularly erstwhile done successful volume. The C.D.C.’s ain sequencing process typically takes astir 10 days to complete aft it receives a specimen.

“We person truly bully surveillance successful presumption of quantity,” said Trevor Bedford, an adept connected viral improvement and surveillance astatine the Fred Hutchinson Cancer Research Center successful Seattle. He added, “But by nature, it lags compared to your lawsuit reporting. And truthful we’ll person bully eyes connected things from 2 weeks ago.”

This benignant of hold is not uncommon successful countries that person a batch of samples to sequence, Dr. Bedford said.

In immoderate states, the timeline is adjacent longer. The Ohio Department of Health notes that, from commencement to finish, the process of “collecting the sample, investigating it, sequencing it and reporting it tin instrumentality a minimum of 3-4 weeks.”


Credit...Pete Kiehart for The New York Times

But present that scientists cognize what they are looking for, they should beryllium capable to expedite the process by prioritizing samples that look astir apt to beryllium Omicron, scientists said.

In 1 tiny spot of luck, Omicron generates a antithetic familial awesome connected P.C.R. tests than the Delta variant, which presently accounts for fundamentally each coronavirus cases successful the United States. (In short, mutations successful the caller variant’s spike cistron means that Omicron samples trial antagonistic for the gene, portion investigating affirmative for a antithetic telltale gene.)

Many labs are present expediting these samples, arsenic good arsenic samples from radical who precocious returned from abroad, for sequencing.

“All of the agencies that are progressive with genomic surveillance are prioritizing those caller travel-associated cases,” Dr. Azarian said.

That whitethorn person been however the California lawsuit was flagged truthful quickly. The diligent returned from South Africa connected Nov. 22 and began feeling sick connected Nov. 25. The idiosyncratic tested affirmative for the microorganism connected Monday and scientists past sequenced the virus, announcing that they had detected Omicron 2 days later.

“The speedy turnaround by the U.S. genomic surveillance strategy is different illustration of however overmuch amended our strategy has go implicit the past fewer months,” Dr. Crawford said.

As overmuch arsenic surveillance has improved, determination are inactive gaps that could dilatory the detection of much cases successful the United States, including tremendous geographic variation.

“Some states are lagging behind,” said Massimo Caputi, a molecular virologist astatine the Florida Atlantic University School of Medicine.

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Over the past 90 days, for instance, Vermont has sequenced and shared much than 30 percent of its microorganism cases and Massachusetts has sequenced much than 20 percent, according to GISAID, an planetary database of viral genomes. Six states, connected the different manus — Kentucky, Pennsylvania, Ohio, South Carolina and Alabama — person each sequenced and reported less than 3 percent of their cases, according to GISAID.

Moreover, scientists tin lone series samples from cases that are detected, and the United States has often struggled to execute capable testing.

“Testing is the weakest portion of our pandemic response,” said Dr. Eric Topol, the laminitis and manager of Scripps Research Translational Institute successful La Jolla, Calif. “It has been from time one.”


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Although testing, similar genomic surveillance, has vastly improved since the aboriginal days of the pandemic, it is inactive highly uneven. And portion rapid, at-home tests person galore advantages, the displacement of immoderate investigating from the laboratory to the location whitethorn contiguous caller challenges for surveillance.

“With expanding at-home accelerated diagnostic tests, if that isn’t followed up with, like, a P.C.R. test, those cases won’t get sequenced,” said Joseph Fauver, a genomic epidemiologist astatine the University of Nebraska Medical Center. The occupation is not insurmountable, helium added, but “maybe there’s a small unsighted spot there.”

There are other, much optimistic reasons that scientists person not detected much cases, though they stay theoretical.

“Perhaps infected patients person mild symptoms, and hence are not getting tested and are not taxable to genomic surveillance,” said Janet Robishaw, the elder subordinate dean for probe astatine the Florida Atlantic University College of Medicine.

(It is still acold excessively aboriginal to know whether Omicron causes illness that is immoderate much oregon little terrible than different variants, scientists stress. Even if the cases are disproportionately mild, which is not yet clear, that could beryllium due to the fact that the variant has mostly infected young oregon vaccinated radical truthful far, who are little apt to make terrible disease.)

It is besides imaginable that determination is not yet overmuch assemblage dispersed of the variant successful the United States. If the cases are mostly isolated, and tied to overseas travel, they could alert nether the surveillance radar.

“We’re benignant of looking for a needle successful the haystack if we’re looking for conscionable azygous cases that are unrelated,” Dr. Azarian said.

Although it is not yet wide wherever Omicron emerged, the archetypal outbreaks were detected successful South Africa, wherever the variant is present widespread.

There are less flights betwixt confederate Africa and the United States than betwixt that portion and Europe, wherever different aboriginal Omicron cases were detected, Dr. Caputi said.

And until aboriginal November, the United States had banned planetary travelers from the European Union and South Africa, helium noted. Even erstwhile officials lifted the ban, travelers from those locations were inactive required to supply impervious of some vaccination and a caller antagonistic Covid test. These measures whitethorn person postponed Omicron’s arrival.

“It is conceivable that Omicron dispersed is lagging down successful the U.S.,” Dr. Caputi said successful an email.

Either way, helium added, helium expected scientists to find much cases soon.

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