> > The country has managed to avoid a variant-fueled spike in coronavirus > cases. Scientists say we were lucky. > > > https://www.nytimes.com/2021/05/14/health/coronavirus-variants-united-states-of-america.html > > > > On Dec. 29, a National Guardsman in Colorado became the first known case > in the United States of a contagious new variant of the coronavirus. > > The news was unsettling. The variant, called B.1.1.7, had roiled Britain, > was beginning to surge in Europe and threatened to do the same in the > United States. And although scientists didn’t know it yet, other mutants > were also cropping up around the country. They included variants that had > devastated South Africa and Brazil > <https://www.nytimes.com/2021/03/03/world/americas/brazil-covid-variant.html> > and > that seemed to be able to sidestep the immune system, as well as others > homegrown in California > <https://www.nytimes.com/2021/01/19/health/coronavirus-variant-california.html>, > Oregon and New York > <https://www.nytimes.com/2021/02/24/health/coronavirus-variant-nyc.html>. > > This mélange of variants could not have come at a worse time. The nation > was at the start of a post-holiday surge of cases that would dwarf all > previous waves. And the distribution of powerful vaccines made by Moderna > and Pfizer-BioNTech was botched > <https://www.nytimes.com/2021/01/17/world/trump-vaccine-doses.html> by > chaos and miscommunication. Scientists warned that the variants — and > B.1.1.7 in particular — might lead to a fourth wave, and that the already > strained health care system might buckle. > > That didn’t happen. B.1.1.7 did become the predominant version of the > virus in the United States, now accounting for nearly three-quarters of all > cases. But the surge experts had feared ended up a mere blip in most of the > country. The nationwide total of daily new cases began falling in April and > has now dropped more than 85 percent from the horrific highs of January. > > > > “It’s pretty humbling,” said Kristian Andersen, a virologist at Scripps > Research in La Jolla, Calif. “We could actually do a lot better than I had > expected.” > > Dr. Andersen and other virus watchers still see variants as a potential > source of trouble in the months to come — particularly one that has > battered Brazil and is growing rapidly in 17 U.S. states. But they are also > taking stock of the past few months to better understand how the nation > dodged the variant threat. > > Experts point to a combination of factors — masks, social distancing and > other restrictions, and perhaps a seasonal wane of infections — that bought > crucial time for tens of millions of Americans to get vaccinated. They also > credit a good dose of serendipity, as B.1.1.7, unlike some of its > competitors, is powerless against the vaccines. > > “I think we got lucky, to be honest,” said Nathan Grubaugh, an > epidemiologist at Yale University. “We’re being rescued by the vaccine.” > > > > After B.1.1.7 emerged at the end of December, new variants with > combinations of troubling mutations came to light. Scientists fretted about > how the competition between the variants might play out. > > > > In January, researchers in California discovered a variant with 10 > mutations that was growing more common there > <https://www.nytimes.com/2021/01/19/health/coronavirus-variant-california.html> > and > had drifted into other states. Laboratory experiments suggested that the > variant could dodge an antibody treatment that had worked well against > previous forms of the virus, and that it was perhaps also more contagious. > > > > In the months that have followed, the United States has drastically > improved its surveillance of how the variants mutate. Last week more than > 28,800 virus genomes, almost 10 percent of all positive test cases, were > uploaded to an international online database called GISAID. That clearer > picture has enabled scientists to watch how the mutants compete. > > The California variant turned out to be a weak competitor, and its numbers > dropped sharply in February and March. It is still prevalent in parts of > Northern California, but it has virtually disappeared from southern parts > of the state and never found a foothold elsewhere in the country. By April > 24, it accounted for just 3.2 percent of all virus samples tested in the > country, as B.1.1.7 soared to 66 percent. > > “B.1.1.7 went in for the knockout, and it’s like, ‘Bye bye, California > variant,’” Dr. Andersen said. > > On the other side of the country, researchers reported in February that a > variant called B.1.526 was spreading quickly in New York and appeared to be > a formidable adversary for B.1.1.7. By February, each of those variants had > grown to about 35 percent of the samples collected by Dr. Grubaugh’s lab in > Connecticut. But B.1.1.7 came out on top. > > In fact, B.1.1.7 seems to have the edge over nearly every variant > identified so far. At a congressional hearing on Tuesday, Dr. Rochelle P. > Walensky, the director of the Centers for Disease Control and Prevention, > said B.1.1.7 made up 72 percent of cases in the country. > > > > “We’re really seeing B.1.1.7 pushing out other variants decisively,” said > Emma Hodcroft, an epidemiologist at the University of Bern. > > The variants identified in California and New York turned out to be only > moderately more contagious than older versions of the virus, and much of > their initial success may have been luck. The overall boom in cases last > fall amplified what might otherwise have gone undetected. > > > > It’s unclear what gives B.1.1.7 an edge over the others. “Is it the > greatest of all the variants? It’s just really hard to say right now,” said > Angela Rasmussen, a virologist at the University of Saskatchewan’s Vaccine > and Infectious Disease Organization. “We need more research to figure out > more about what all of these combinations of mutations are doing.” Some > answers may come from California, where researchers are staging a > head-to-head competition in a lab, injecting mice with a cocktail of > B.1.1.7 and six other variants. > > “The idea is to see which one will win out,” said Dr. Charles Chiu, a > virologist at the University of California, San Francisco, who was the > first scientist to discover the California variant. > > In Michigan, one of the few states that saw the predicted surge in cases > this spring, B.1.1.7 found a hook in younger people who were returning to > schools and playing contact sports. > > “Because it’s more transmissible, the virus finds cracks in behavior that > normally wouldn’t have been as much of a problem,” said Emily Martin, an > epidemiologist at the University of Michigan. > > > > But in the rest of the country, people naturally became more cautious when > confronted with the horrifying toll of the virus after the holidays. > B.1.1.7 is thought to be about 60 percent more contagious than previous > forms of the virus, but its mode of spread is no different. Most states had > at least partial restrictions on indoor dining and instituted mask mandates. > > “B.1.1.7 is more transmissible, but it can’t jump through a mask,” Dr. > Hodcroft said. “So we can still stop its spread.” > > But other experts are still discomfited by how much the virus seems to > have defied predictions. > > “I can’t necessarily ascribe it just to behavior,” said Sarah Cobey, an > evolutionary biologist at the University of Chicago. Respiratory viruses > sometimes go through seasonal cycles, but it’s not clear why the > coronavirus’s cycle would have caused it to decline in the middle of > winter. “That makes me feel maybe even more ignorant,” she said. > > Also puzzling is why variants that pummeled other countries have not yet > spread widely in the United States. B.1.351 rapidly dominated South Africa > and some other African countries late last year. It was first reported > <https://www.nytimes.com/2021/01/28/us/covid-south-africa-variant-south-carolina.html> > in > the United States on Jan. 28, but still accounts for only 1 percent of > cases. That may be because it can’t get ahead of the fast-spreading B.1.1.7. > > “I think that is because it doesn’t really have much transmission > advantage,” said William Hanage, an epidemiologist at the Harvard T.H. Chan > School of Public Health. > > > > P.1, a variant that is ravaging Brazil, got off to a slow start in the > United States but is now estimated > <https://outbreak.info/situation-reports?pango=P.1&loc=BRA&loc=USA&loc=USA_US-CA&selected=USA> > to > make up more than 10 percent of the country’s cases. > > > > “I believe it is a matter of time before the P.1 variant becomes one of > the most prevalent in the U.S.A.,” warned Dr. André Ricardo Ribas Freitas, > a medical epidemiologist at Faculdade São Leopoldo Mandic in Brazil. > > Still, Nels Elde, an evolutionary biologist at the University of Utah, > said the events of the past four months raised questions about whether it > was worth fretting over different variants, rather than focusing on the > behaviors that can rein in all of them. > > “We’re splitting hairs between a handful of mutations here and there, > we’ve lost some perspective,” he said. “It’s catnip for a curious mind.” > > The United States also has an ample supply of powerful vaccines that make > variants more an academic concern than a cause of worry for the average > person. The vaccines may be slightly less effective against the variants > identified in South Africa and Brazil, but they prevent severe disease from > all known variants. > > *It’s not impossible that the situation could worsen. Only about 35 > percent of people in the United States have been fully immunized > <https://www.nytimes.com/interactive/2020/us/covid-19-vaccine-doses.html>, > and the protection from the vaccines may wane by the winter. No one knows > how variants emerging in other parts of the world, like one that has come > to prominence in India and is circulating at low levels in the United > States, will behave here. And yet more variants will inevitably arise in > places where the virus is rampant, Dr. Cobey warned: “There’s a lot of > evolution to happen yet.”* > > >
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