Here’s What You Need to Know About the Multiple New Coronavirus Strains in the U.S.

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Editor’s Note: New details about these variants are emerging as researchers continue to learn more. While we aim to update this article as soon as new information becomes available, please check the CDC website for the latest details about variants in the United States.

On January 18, 2021, Los Angeles-based healthcare organization Cedars-Sinai released a statement detailing a new strain of the novel coronavirus, dubbed CAL.20C, that researchers believed may have been responsible for the marked surge in COVID-19 cases that subsequently took place across Southern California. By the middle of January, Los Angeles County had reported more than 14,000 COVID-19 deaths since the beginning of the coronavirus pandemic and over 1 million COVID-19 cases in that same time frame — with two-thirds of those cases occurring since November of 2020.

Cedars-Sinai researchers also found that CAL.20C was present in 36.4% of patients who tested positive for COVID-19 between November 22, 2020, and December 28, 2020 — and CAL.20C "was almost nonexistent in October" of that same year. The emergence of CAL.20C, which researchers believe originated in Southern California, may seem shocking. That’s not only because it appears to be spreading so rapidly, but also because it appeared at all.

CAL.20C is a variant — a virus that’s experienced mutations, which are changes to the virus’ structure that can alter how it functions — of SARS-CoV-2, the specific coronavirus that causes the disease COVID-19. Mutations can cause viral variants to behave differently than previous strains of the same virus. This may spark changes in everything from how the viruses are transmitted to the ways vaccines work against them, and these changes happen spontaneously as the virus spreads. That the resulting variants can also have unforeseen consequences is cause for concern during a pandemic that’s barely under control.

Another reason why CAL.20C feels so urgent? Aside from its rapid spread, it isn’t the only SARS-CoV-2 variant the United States is contending with. Others have emerged over the past year, with several notable strains spreading rapidly during last few months. It’s still somewhat unclear exactly how these variants may impact our efforts to contain the virus, but research into them, which can better inform our pandemic response, is ongoing. With that in mind, here’s what we know so far about the variants spreading in the United States.

What Are the Current Variants Affecting the United States?

Variants of SARS-CoV-2 have been circulating the globe since the beginning of the pandemic. However, in recent months — primarily since the fall of 2020 — new variants appear to be emerging at faster rates. These are some of the prominent variants circulating in the United States, along with the basics scientists know about them so far.

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D614G - This variant isn’t recent, but it’s one worth mentioning because of the trajectory it took after emerging. D614G appeared in late January or early February of 2020 as a mutation of the original form of SARS-CoV-2 first identified in China. This variant’s mutations affected the virus’ spike proteins, which attach the virus to human cells so it can begin replicating. The mutations also made those spike proteins better able to enter cells. According to the World Health Organization (WHO), "compared to the initial virus strain, the strain with the D614G substitution has increased infectivity and transmission," meaning this variant’s mutation made it more efficient at both replicating in a host and moving from person to person.

Why is this significant? D614G, by the summer of 2020, had become (and remains) the dominant strain circulating around the world. This variant "[did] not cause more severe illness or alter the effectiveness of existing laboratory diagnostics, therapeutics, vaccines or public health preventive measures," explains the WHO. But, D614G’s spread illustrates the possibility of a mutation to "confer an advantage to the virus as it infects people and invades their cells," note global health policy experts Anna McCaffrey and J. Stephen Morrison. "Those advantaged strains may become dominant, making outbreaks [involving variants] far more difficult and costly to control."

B.1.1.7. - Also called VOC 202012/01, this strain first emerged in Southeast England as early as September of 2020. Since then it has become the dominant strain in England and has spread to dozens of countries across the world, including the United States. This variant’s spike protein carries eight different mutations in addition to several other genetic changes that have made this form of the virus more efficient at attaching to cells.

According to the Centers for Disease Control and Prevention (CDC), evidence indicates that this variant is transmitted more efficiently and rapidly than other strains of SARS-CoV-2; it’s about 56% more transmissible. However, preliminary reports from the WHO also indicate that B.1.1.7. doesn’t result in more severe symptoms or a higher incidence of death than other variants. Using modeling software, public health experts initially predicted that, by March of 2021, this variant would become the dominant strain in the United States. And, as of early April, this prediction came true; B.1.1.7. "is now the most common lineage circulating in the United States."

Ohio Variants - First discovered by researchers at Ohio State University’s Wexner Medical Center, one variant called COH.20G/501Y initially emerged in Ohio in early January. It has the exact same mutations as B.1.1.7., but scientists believe that this variant developed in the United States, independently of the U.K. strain. COH.20G/501Y was only found in one patient initially, and researchers are unsure how prevalent this variant is. However, because of its similarities to B.1.1.7. in terms of mutations, it may be COH.20G/501Y more contagious.

Wexner Medical Center scientists also discovered another new regional variant, which remains unnamed but has become the dominant form of the virus circulating in Columbus and surrounding areas. This variant has "three other gene mutations not previously seen together in SARS-CoV-2," according to a press release from the medical center’s researchers, and these mutations also affect the spike proteins on the surface of the virus. While it remains unclear exactly how transmissible this variant is, researchers believe it’s more infectious based on how quickly it’s spread since emerging in late December of 2020.

CAL.20C - One case of this variant was initially detected in a batch of virus samples from Los Angeles County in July of 2020, and it quickly began spreading in November of that year. This variant, which contains five distinct mutations, is now present in more than half of the cases in Los Angeles after surging over the winter holidays, according to The New York Times. CAL.20C has spread to a number of other states in the country and has been detected as far away as Washington, D.C.

While researchers note there’s no evidence that this variant is more lethal, it does appear to be more contagious; three of its mutations affect its spike proteins. Research is ongoing to definitively determine whether CAL.20C is more transmissible or resistant to antibodies. Interestingly, this variant may be responsible for a recent group of cases affecting the troop of gorillas living at the San Diego Zoo Safari Park.

B.1.351 - This strain, which is also known as the South African variant, was initially detected in that country in October of 2020 and first appeared in the United States in late January of 2021. B.1.351 shares several of the same mutations as B.1.1.7., despite having emerged independently of B.1.1.7. It quickly began to spread around the world and appears to be more infectious, again due to spike protein mutations that give this variant an advantage in attaching to and infecting human cells. While the CDC notes that there's currently no evidence this variant causes more severe cases of COVID-19, preliminary research suggests B.1.351 may evade full protection from the Pfizer vaccine.

P.1 - Also known as the Brazilian variant, this strain was first detected in mid-January in four travelers from the Amazon rainforest visiting Japan. By the end of that month, the variant was present in the United States and may have been responsible for an earlier surge in infections in Brazil. In addition to spike protein mutations that may make this variant more contagious, P.1 contains a mutation called E484K, which may help the virus evade antibodies. This means immunity, whether developed from experiencing a previous COVID-19 infection or receiving one of the vaccines, may not provide sufficient protection against severe reinfection in people exposed to the P.1 variant.

Is the Emergence of Variants Cause for Concern?

Scientists have long expected that variants would emerge during the pandemic — it’s well-established that RNA viruses like SARS-CoV-2 mutate frequently. But it’s the potential harmful consequences variants can introduce — and the fact that researchers won’t necessarily know what those consequences are until they’ve started affecting many people — that could be concerning. The CDC has outlined some of those possible consequences and what they involve. These include a variant’s:

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  • Ability to spread faster among people
  • Ability to cause milder or more severe symptoms and disease
  • Ability to go undetected by diagnostic tests
  • Ability to evade immunity induced by vaccines or natural infection
  • Decreased response to available treatments


Despite these potential effects, "not all [variants] are a cause for concern," notes Dr. Angela Rasmussen, a virologist at Georgetown University’s Center for Global Health Science and Security. "We should worry when a variant is accompanied by epidemiologic evidence such as that observed in the U.K.," Dr. Rasmussen said in reference to the region’s surge in cases following the emergence of the B.1.1.7. variant. Infectious disease expert Dr. Anthony Fauci further explained this, saying, "If you have a virus that's more transmissible, you're going to get more cases… When you get more cases, you're going to get more hospitalizations, and when you get more hospitalizations, you ultimately are going to get more deaths."

Ultimately, unless a variant’s health effects are more damaging or pronounced, it isn’t necessarily something to worry about. But the frequency with which variants are now emerging — and the fact that they appear to be more transmissible — may be.

Why Are These Variants Emerging?

COVID-19 continues to spread in the United States even as more people become vaccinated, and this unrestrained transmission is a primary contributing factor for the emergence of new variants. According to Dr. Ben Bimber, research professor at Oregon Health and Science University, each time the virus has an opportunity to replicate — the process it undergoes when it enters a new host and begins infecting cells — it also has an opportunity to mutate.

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Mutations often don’t affect the virus in any meaningful way. But they can also transform the virus into a variant that exhibits "increased disease severity," explains Dr. Rasmussen. The more a virus spreads, the more chances it has to mutate into a variant that’s potentially more harmful than or that has a survival advantage over previous strains.

This increased likelihood of mutations corresponding with the surge of cases across the U.S. highlights the importance of working to slow person-to-person COVID-19 transmission. "The only way to stop emergence of new variants is to stop the spread of the virus," Dr. Bimber told NBC News. "If there’s more people infected, there’s simply more virus out there and it has more opportunities to mutate."

But it can take several months to identify variants and determine if they’re causing surges. This time frame, coupled with the unknown and potentially harmful ways mutations could alter the virus, are worrisome. Fortunately, according to Dr. Dan Jones of Ohio State University’s Wexner Medical Center, there’s a clear pathway to preventing variants from spreading and keeping new variants from surfacing: getting vaccinated.

What Do the Variants Mean for Current Vaccines?

That a variant could emerge that would resist vaccine-induced immunity is a potential consequence researchers and health organizations are concerned by. And because many of the current variants have only begun a more drastic spread within the last few months, researchers are still investigating the strains’ impact on current vaccines.

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Several smaller studies indicate "some variants may pose unexpected challenges to the immune system, even in those who have been vaccinated." However, these studies are based on laboratory blood tests and may not accurately illustrate real-world viral spread or variant responses to the available vaccines. In addition, researchers are finding that the Oxford-AstraZeneca vaccine, which the WHO approved for emergency use in mid-February, may not be as effective at protecting against variants. This news comes after a new study showed preliminary results that the Oxford-AstraZeneca vaccine only offers "minimal protection" against the variant of the coronavirus that first appeared in South Africa.

Dr. Fauci has also acknowledged that the variants "could potentially weaken the effectiveness of current vaccines." Additionally, "the vaccines may not prevent people from becoming mildly or asymptomatically infected with the variants," Dr. Michel Nussenzweig, an immunologist at New York’s Rockefeller University, told The New York Times. U.S. health organizations will need to perform more genetic sequencing to determine what the changes in the variants mean for vaccine efficacy.

Pfizer, Moderna, Johnson and Johnson and AstraZeneca are continuing to release data about the efficacy of their respective vaccines on the variants as this new information comes to light. Generally, their vaccines appear as though they may not be as effective against the South African variant, but clinical studies are ongoing and much more research is needed to determine the vaccines' response to the Brazilian variant.

But there may be a silver lining: There’s a "‘cushion effect,’ meaning current vaccines will still offer some protection and will still be far better than no vaccine at all," according to USA Today. Dr. Nussenzweig echoed this point: "Existing vaccines will still prevent serious illness, and people should continue getting them." Until we’re all able to get vaccines, however, it’s important that we take the right steps to slow the spread of COVID-19 variants so we can limit opportunities for mutations to occur — and keep ourselves healthy.

How Can You Protect Yourself — and Others?

Researchers are continuing to discover new information about the multiple coronavirus variants present in the United States. They’re still working to learn whether — and how — the diseases that these variants cause could differ from COVID-19 and how those diseases might respond differently to current treatment protocols and vaccines.

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Although the variants seem to be more transmissible, one thing health experts are confident about is that these mutated forms still spread in the same way that all coronaviruses transfer from person to person. When someone who has the virus coughs, sneezes, talks, breathes or sings, they release respiratory droplets containing the virus into the air. These small droplets can land in the mouths, eyes or noses of people nearby, who then contract the virus.

So what does this mean in terms of protecting yourself against the new variants? "All the things we have learned about this virus still apply," Dr. Ashish K. Jha, dean of Brown University’s School of Public Health, told The New York Times. "It’s not like this variant is somehow magically spreading through other means. Anything risky under the normal strain just becomes riskier with the variant." Because the virus spreads in the same way, the steps we’ve been taking all along to protect ourselves from the novel coronavirus remain largely unchanged.

But because the variants appear more infective, notes Tara Parker-Pope of The New York Times, we may need to become "more rigorous" in our adherence to protective measures. That’s particularly important if we’ve grown "lax about our COVID-19 safety precautions" after nearly a year of following guidelines and grappling with pandemic fatigue. To protect yourself effectively and reduce transmission, work to become more vigilant about following these CDC-recommended guidelines:


  • Wear a two- or three-layer mask made of washable fabric that covers your nose and mouth and doesn’t gape at the sides. Always wear your mask in public settings or when you’re around people you don’t live with.
  • Practice physical distancing. Stay 6 feet away from people who don’t live in your household at all times, particularly when you’re in public places.
  • Avoid crowds and crowded areas, such as bars and restaurants. Stay out of poorly ventilated spaces like enclosed rooms with no airflow, which are where the virus is more likely to spread.
  • Sanitize high-touch surfaces, such as computer keyboards and doorknobs, with a recommended disinfectant at least daily or more often.
  • Wash your hands frequently for at least 20 seconds using soap and water. Or, use hand sanitizer that contains at least 60% alcohol. It’s especially important to clean your hands after touching your mask, coughing, sneezing, blowing your nose or going in public.


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