Microscope image of virus

The emergence of what appear to be faster-spreading variants of the coronavirus is increasing concern about the virus’s path just as the vaccines that many hope will bring an end to the pandemic are being distributed.

The variant causing the most alarm was first found in England, leading to new travel restrictions on travelers from the U.K. and as of Monday, a major new national lockdown in that country. But it has now been detected in as many as 30 counties, including the U.S. The first known U.S. case was identified on on Dec. 29, in Colorado, in someone with no travel history. Another case was found the next day in San Diego. New York announced its public health laboratory has identified a case on Monday, also in someone with no travel history.

Anthony Fauci, MD, director of the National Institute of Allergy and Infectious Diseases, told PBS Newshour last week that the variant “doesn't seem at all to have any impact on the virulence or what we call the deadliness of the virus. It doesn't make people more sick. And it doesn't seem to have any impact on the protective nature of the vaccines that we're currently using.” 

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The U.S. now requires that people arriving here from the United Kingdom by plane test negative by a PCR or antigen test no more than 72 hours before departure.

Infectious disease experts note that viruses always mutate. This virus, like many others, constantly acquires and loses genetic traits as it spreads.

“I would not be surprised of the existence of additional novel strains within the populace, ones that have yet to be identified,” says James Dickerson, PhD, chief scientific officer for Consumer Reports.

Here’s what we know about the variants causing concern now. 

Why Do Viruses Mutate?

Viruses like SARS-CoV-2, which causes COVID-19, make imperfect copies of themselves as they spread from person to person or from an animal to a person, leading to constant mutations and new variants, says Peter Katona, MD, an infectious disease specialist and clinical professor of medicine at the David Geffen School of Medicine at UCLA. These mutations often don’t provide any advantage to the virus. But sometimes, a mutation can make a virus more transmissible or change the severity of the disease the virus causes.  

How Has the Coronavirus Mutated?

The SARS-CoV-2 virus first emerged in China and continued to mutate as it spread around the globe. A variant that was likely more contagious emerged in Europe, Katona says. That variant’s infectiousness helped it spread rapidly throughout Europe and the U.S., where it became one of the most dominant strains.

The variant under investigation in the U.K. has a large number of mutations, according to the ECDC report, including changes to the spike protein that the coronavirus uses when infecting cells. After comparing the number of coronavirus cases in the U.K. with cases predicted by computer models, scientists there think this variant is approximately 56 percent more infectious than existing variants.

But while these models seem to indicate that the new variant is spreading more quickly than previous strains of the virus, people traveling for the holidays could also account for some of the higher case figures. Scientists need more data before they’ll know how much more infectious this variant truly is, says Gregory Poland, MD, a professor of medicine and infectious diseases, and director of the Vaccine Research Group at the Mayo Clinic.

There’s no data indicating that this variant of the virus causes people to become sicker. But a more infectious variant would lead to more deaths and severe cases in the long run, since cases could grow exponentially, putting already strained hospital systems under further pressure, Poland says.

Where Are Current Mutations Spreading?

Cases of the variant that’s under investigation in the U.K. are primarily in Kent, regions of London, and wider southeast England, according to the ECDC. But this version has also been identified in Wales, Denmark, Belgium, The Netherlands, Australia, Canada, and elsewhere, indicating that it has spread internationally as well. The first known case in the U.S. was identified on Dec. 29, in Colorado, in someone with no travel history.

Other countries, including the U.K., do more routine virus sequencing than the U.S., which makes it difficult to know how widespread the variant may be here. (Sequencing is the kind of analysis scientists do to determine the variant of a virus causing a particular case, or a partcular outbreak.) Viruses have been sequenced in just 51,000 of the 17 million COVID-19 cases in the U.S., according to CDC.

With this new variant now in the U.S., public health officials are already ramping up their sequencing efforts, Gregory Armstrong, MD, the director of the Office of Advanced Molecular Detection at the Centers for Disease Control and Prevention (CDC) said Dec. 30, with the goal of sequencing 3,000 viruses a week soon. That data should help provide a clearer picture of how widespread the variant is in the U.S.

If this variant does prove to be more contagious, people should expect it to spread further, Katona and Poland say.

While the large number of mutations in this variant have raised questions about how it emerged, it’s not the only virus variant that scientists are investigating. An evolutionarily distant variant with some similar mutations is spreading rapidly in South Africa, according to the ECDC, which could indicate that mutations like this aren't uncommon. 

Are Children More Affected by the New Variant?

Some data has indicated that younger kids may be less contagious when infected with COVID-19, though more research on the topic is needed. In general, kids have been more likely to have asymptomatic or milder forms of the disease, according to the CDC, though they can catch, spread, and be severely affected by it.

However, rapidly rising rates of infection among young people in the U.K. have many wondering whether the new strain may be more contagious for kids, increasing the likelihood of transmission overall and making schools riskier. 

"The rate of confirmed infection in children is at its highest yet," Christophe Fraser, Ph.D., an infectious disease epidemiologist at Oxford's Big Data Institute and professor in the Nuffield Department of Medicine, noted on Twitter. On Monday, U.K. Prime Minister Boris Johnson announced that schools and colleges in that country would close as the U.K. tries to get the current outbreak under control.

Some preliminary data indicate that the new variant may cause people to carry a higher viral load, essentially meaning that they could have more viral particles to spread to others, according to Poland at the Mayo Clinic. If that is the case, it could be the cause of this variant's seemingly high infectiousness. If children carried lower viral loads of previous variants of the coronavirus, but higher loads of this one, that could explain why rates of infection among kids are rising, he says—but adds that we need more research to confirm whether or not that's the case.

How Might Mutations Affect the Vaccine?

Vaccines teach our immune system to respond to a virus by recognizing some key sign of it. Mutations that affect the parts of the virus the immune system recognizes can help a virus thwart a vaccine’s effectiveness.

The first vaccines that have been authorized in the U.S. for COVID-19, made by Moderna and a partnership of Pfizer and BioNTech, target a particular protein—the spike protein—that the coronavirus uses to infect people. So mutations of that protein could potentially make a vaccine less effective, Poland says.

But even if the mutations in current variants of the virus have some impact on the vaccines' efficacy, it’s likely that the vaccines could still be highly effective, he says.

Still, we may eventually need new vaccines that target other parts of the SARS-CoV-2 virus, Poland wrote in a commentary for the journal Vaccine, where he’s the editor. 

What Should You Do?

The same advice about stopping the spread of the virus is even more crucial if this mutation spreads faster. “The appropriate action is caution, follow the existing procedures for mask wearing, social distancing, and minimizing the number of potential lines of exposure,” says CR’s Dickerson.

The more the coronavirus spreads, the more it mutates, according to Poland and Katona.

“We are needlessly prolonging the duration and the severity of this pandemic by not following a simple hands, face, space paradigm,” Poland says. 

Editor's Note: This story has been updated to include new information as developments change. It was originally published Dec. 22, 2020.