COVID-19 Variant Updates for the United States

COVID-19 vaccines arrayed in rows of small glass vials

By Ruth Werner

If you’re like me, you have seen in the news that SARS-CoV-2, the virus that causes COVID-19, has developed some evolutionary descendants, and those descendants are potentially threatening. And maybe you’re a little worried about that. But trying to keep up with the latest information about the virus can feel overwhelming, especially since every single day we seem to hear about new mutations from California, or a dangerous variant from New York, and the UK variant, and South African, and Brazilian, and now . . . a double mutation in India?

Well, I have undertaken to dig up and explain what is going on in this world of virus evolution, and I can tell you that as of the third week of March 2021, this information is up-to-date and as accurate as I can make it. I have heavily relied on helpful information from the Centers for Disease Control and Prevention (CDC), the New York Times, a publication from Australia called The Conversation, and interviews with Dr. Peter Hotez, dean for the National School of Tropical Medicine and professor in the Departments of Pediatrics and Molecular Virology and Microbiology at Baylor College of Medicine, as well as dozens of other credentials. (Links to these resources are provided for interested readers who would like to learn more.)

Mutation(s) -> Variant -> Strain

Before we dig into new viral diversity, let’s review a little bit of vocabulary, because the terms mutation, variant, and strain are all used in the press, but they are not interchangeable.

You are probably aware that SARS-CoV-2 is the virus that causes COVID-19, and that it is composed of long strands of RNA (ribonucleic acid). The virus works by invading target cells (the ones with ACE-2 receptor sites) and reconfiguring the cellular machinery to produce more copies of virus. In this process, the new RNA molecules often accumulate teeny tiny errors. These are mutations.

Sometimes the mutations are meaningless, and they make no difference at all. Sometimes mutations mess up some internal mechanisms of the virus and cause it to die off—we like those mutations. Sometimes mutations accrue in viruses that make them genetically distinct from the original virus. We call these variants. Variants can be the result of one or many different mutations, and they are passed on to future generations of the virus.

And sometimes mutations, or groups of mutations, give variants some new capacities or different behaviors. These are also passed on through generations of viral replications, giving rise to a pathogen that is significantly different from the original virus. We call these new pathogens viral strains. So, mutations sometimes lead to variants. If the variants have different capacities or behaviors from the original virus, we call them strains.

Technically the “variants” that are discussed in the US right now could be called “strains,” but this is a fine point of semantics that isn’t really worth pursuing.

Viral variants or strains are identified when they are genetically sequenced. In the US, this is done by the CDC National SARS Strain Surveillance system (NS3). This organization collects samples from tests all over the country and analyzes them for the presence of mutations and variants. Not every sample is tested, however, so the reported numbers and locations of SARS-CoV-2 variants reflect what has been found, but not necessarily what is really present. The US Food and Drug Administration (FDA) is keeping a close eye on variants in the US, specifically to watch for whether it will become necessary to update the mRNA vaccines or plan for a booster to reduce risk of hospitalization or mortality.

CDC Classifications

The CDC classifies the variants as variants of interest, variants of concern, and variants of high consequence.

  • Variants of interest. These are variants that are associated with characteristics that change how they bind to cell receptors, or they have reduced sensitivity to antibody activity, or other qualities that distinguish them from the original virus. Right now, we have three variants of interest being tracked to see if they become a greater concern.
  • Variants of concern. These are variants that show increased transmissibility and a risk of more severe disease than the original virus. They may also be resistant to some treatment or prevention mechanisms. There are five variants of concern in the US at this moment, and they are discussed below.
  • Variants of high consequence. These are variants that would require new prevention measures or medical treatments. As of this writing, we have no new variants of high consequence (phew!).

Variants of Concern

At this point, we have five major strains in the US (although they are often called variants—see point above about semantics) in addition to the original SARS-CoV-2 virus.


This strain was first identified in the UK, so it is sometimes called the UK variant. It is spreading quickly in the US; it has been seen in 49 states so far. (Only Oklahoma has not reported any cases with B.1.1.7 so far.)

The B.1.1.7 variant is expected to become the dominant strain in the US by late spring. It is about 50 percent more infectious than the original version of the virus; this may be because its mutations allow it to cling to ACE 2 receptors more efficiently. It is also seen to have a mortality rate about 35 percent higher than the original virus.

Because the B.1.1.7 variant is more infectious and more deadly, some experts, including Dr. Fauci, now recommend double-masking or using high quality N95 or KN95 masks. (View this New York Times article for more on the challenge of finding good-quality masks—it’s much harder than making a quick visit to your favorite mail order service.)


This strain was first identified in South Africa, where it quickly became the dominant strain in that country and on much of the rest of the African continent. For reasons that are not clear, it is not spreading as fast in the US as B.1.1.7. At this point B.1.351 has been identified in 27 states.


This strain was first identified in Japan, among some travelers from Brazil. For this reason, it is sometimes called the Brazilian variant, and it is the dominant strain in that country. Evidence suggests that P.1 can evade antibodies more easily than the other variants. This explains why some areas in Brazil (where herd immunity to the original virus was reached) had many cases of reinfection with this new version of the virus. The P.1 strain has been found in 18 states so far.

B.1.427 and B.1.429

These variants arose in California. They are both slightly more transmissible and they are more resistant to some treatment options than the original virus. The CDC is not reporting nationwide numbers on these yet. 

What Can We Do?

These viral strains will almost certainly not be the last ones we see. We daily get reports of new mutations here and around the world, and if any of them take hold, then we will have new variants and strains to address.

The best thing we can do to limit the spread of viral variants and strains in the US is to get vaccinated as soon as possible, and to continue to observe physical distancing, to use masks, and to observe good hygienic practices. All of the available vaccines show consistent, reliable protection against developing severe illness with hospitalization and the risk of death for all of the variants so far.

For more on vaccines, read this previous blog post on The sooner we achieve herd immunity, the sooner the variants will have no more hosts to invade, and we can all think about a post-COVID life. In the meantime, don’t stop your sensible, virus-limiting behaviors. The finish line is in sight, but we haven’t reached it yet.


Berg, S. “What Doctors Wish Patients Knew about New Coronavirus Variants.” American Medical Association. Accessed March 3, 2021.

Centers for Disease Control and Prevention. “About Variants of the Virus that Causes COVID-19.” Accessed March 2021.

Centers for Disease Control and Prevention. “Genomic Surveillance for SARS-CoV-2 Variants.” Accessed March 2021.

Centers for Disease Control and Prevention. “SARS-CoV-2 Variant Classifications and Definitions.” Accessed March 2021.

Centers for Disease Control and Prevention. “Science Brief: Emerging SARS-CoV-2 Variants.” Accessed March 2021.

Centers for Disease Control and Prevention. “US COVID-19 Cases Caused by Variants.” Accessed March 2021.

Centers for Disease Control and Prevention. “Variant Proportions in the US.” Accessed March 2021.

Chen, B. X. “How to Buy a Real N95 Mask Online.” February 17, 2021. The New York Times.

Corum, J. and C. Zimmer. “Coronavirus Variants and Mutations.” The New York Times. Accessed March 1, 2021.

Madzokere, E. and L. Herrero. “What’s the Difference Between Mutations, Variants and Strains? A Guide to COVID Terminology.” The Conversation. Accessed March 1, 2021.

Short, K.  “UK, South African, Brazilian: A Virologist Explains Each COVID Variant and What They Mean for the Pandemic.” The Conversation. Accessed March 3, 2021.

Zimmer, C. “Covid-19: The U.S. Has Its Own New Worrisome Variants.” February 14, 2021. The New York Times.

author bio

Ruth Werner is a former massage therapist, a writer, and an NCBTMB-approved provider of continuing education. She wrote A Massage Therapist’s Guide to Pathology (available at now in its seventh edition, which is used in massage schools worldwide.