WASHINGTON — A highly infectious variant of the
coronavirus that was first identified in Britain has become the most common
source of new infections in the United States, the director of the Centers for
Disease Control and Prevention said Wednesday. The worrisome development comes
as officials and scientists warn of a possible fourth surge of infections.
اضافة اعلان
Federal health officials said in January that the
B.1.1.7 variant, which began surging in Britain in December and has since
slammed Europe, could become the dominant source of coronavirus infections in
the United States, leading to a huge increase in cases and deaths.
At that point, new cases, hospitalizations and deaths
were at an all-time high. From that peak, the numbers declined until late
February, according to a New York Times database. After several weeks at a
plateau, new cases and hospitalizations are increasing again. The average
number of new cases in the country has reached nearly 65,000 a day as of
Tuesday, concentrated mostly in metro areas in Michigan as well as in the New
York City region. That is an increase of 19% compared with the figure two weeks
ago.
Dr. Rochelle Walensky, the CDC director, who warned last
week that she felt a recurring sense of “impending doom,” said Wednesday that
52 of the agency’s 64 jurisdictions — which include states, some major cities
and territories — are now reporting cases of these so-called “variants of
concern,” including B.1.1.7.
The number of deaths, however, continue to decline —
potentially a sign that mass vaccinations are beginning to protect older
Americans and other highly vulnerable populations.
“These trends are pointing to two clear truths,”
Walensky said. “One, the virus still has hold on us, infecting people and
putting them in harm’s way, and we need to remain vigilant. And two, we need to
continue to accelerate our vaccination efforts and to take the individual
responsibility to get vaccinated when we can.”
B.1.1.7, the first variant to come to widespread
attention, is about 60% more contagious and 67% more deadly than the original
form of the coronavirus, according to the most recent estimates. The CDC has
also been tracking the spread of other variants, such as B.1.351, first found
in South Africa, and P.1, which was first identified in Brazil.
The percentage of cases caused by variants is clearly
increasing. Helix, a lab testing company, has tracked the relentless increase
of B.1.1.7 since the beginning of the year. As of April 3, it estimated that
the variant made up 58.9% of all new tests.
That variant has been found to be most prevalent in
Michigan, Florida, Colorado, California, Minnesota and Massachusetts, according
to the CDC. Until recently, the variant’s rise was somewhat camouflaged by
falling infection rates overall, leading some political leaders to relax
restrictions on indoor dining, social distancing and other measures.
As cases fell, restive Americans headed back to school
and work, against the warnings of some scientists.
Federal health officials are tracking reports of
increasing cases associated with day care centers and youth sports, and
hospitals are seeing more younger adults — people in their 30s and 40s who are
admitted with “severe disease,” Walensky said.
It is difficult for scientists to say exactly how much
of the current patterns of infection are because of the growing frequency of
B.1.1.7.
“It’s muddled by the reopening that’s going on and
changes in behavior,” said Dr. Adam Lauring, a virologist at the University of
Michigan.
But he noted that people were becoming less cautious at
a time when they should be raising their guard against a more contagious
variant. “It’s worrisome,” he said.
At the same time, the United States is vaccinating an
average of about 3 million people a day, and states have rushed to make all
adults eligible. The CDC reported on Wednesday that almost 110 million people
had received at least one dose of a COVID-19 vaccine, including about 64.4
million people who have been fully vaccinated. New Mexico, South Dakota, Rhode
Island and Alaska are leading the states, with about 25% of their total
populations fully vaccinated.
Scientists hope that vaccination will blunt any
potential fourth surge.
On Tuesday, President Joe Biden moved up his vaccination
timetable by two weeks, calling states to make every U.S. adult eligible by
April 19. All states have already reached or expect to exceed this goal after
he initially asked that they do so by May 1.
The B.1.1.7 variant first arrived in the United States
last year. In February, a study that analyzed half a million coronavirus tests
and hundreds of genomes predicted that this variant could become predominant in
the country in a month. At that time, the CDC was struggling to sequence the
new variants, which made it difficult to track them.
But those efforts have substantially improved in recent
weeks and will continue to grow, in large part because of $1.75 billion in
funds for genomic sequencing in the stimulus package that Biden signed into law
last month. By contrast, Britain, which has a more centralized health care
system, began a highly promoted sequencing program last year that allowed it to
track the spread of the B.1.1.7 variant.
“We knew this was going to happen: This variant is a lot
more transmissible, much more infectious than the parent strain, and that
obviously has implications,” said Dr. Carlos del Rio, a professor of medicine
and an infectious disease expert at Emory University. In addition to spreading
more efficiently, he said, the B.1.1.7 strain appears to cause more severe
disease, “so that gives you a double whammy.”
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