Variants of COVID-19 Are Spreading Across the U.S.

An illustration of a United States map in light blue-green on a blue background; lighter pale yellow-white circles suggest areas of attention.


Key Takeaways

  • Variants of the COVID-19 virus that are more easily transmissible are spreading in the United States. One of the variants, B.1.1.7, also causes a more severe illness than the virus that first circulated.
  • The spread of the variants combined with the relaxation of quarantine measures in some states has caused an uptick in new COVID cases, offsetting months of progress.
  • The best way to control the spread of the new variants is by getting a larger percent of the population vaccinated against COVID-19.

The number of COVID-19 cases caused by variants of the SARS-CoV-2 virus has been increasing rapidly in many parts of the United States. Some of the variants are more easily spread than the virus that circulated at the start of the pandemic, which is fueling the rise in cases this spring.

Daniel C. DeSimone, MD, associate professor of medicine at the Mayo Clinic College of Medicine and Science, tells Verywell that one variant currently in the U.S. is the B.1.1.7 variant, which was first seen in the United Kingdom.

The U.K. variant is a variant of concern because not only is it more transmissible, but also may cause more severe COVID illness.

The variants that have been found in the U.S. so far are:

  • B.1.1.7—first identified in the U.K.
  • B.1.351 —first identified in South Africa
  • P.1—first identified in Japan and Brazil
  • B.1.427 and B.1.429 —first identified in California

States with Most Variant Cases

As of the first week of April, the Centers for Disease Control and Prevention (CDC) has identified five states with the highest number of COVID-19 cases caused by the new variants (most of which have been attributed to B.1.1.7.): Florida, Michigan, Minnesota, Massachusetts, and California.

All viruses mutate and do so frequently, but some mutations are more worrisome than others. For now, the CDC is keeping its eye on "variants of concern"—those that make a virus behave differently in significant ways, such as by making it more easily spread or capable of causing severe illness.

More Easily Spread

DeSimone, who is also an infectious disease specialist at the Mayo Clinic, says that the U.K. variant spreads more easily and might be more likely to cause death than the initial COVID virus.

According to DeSimone, the U.K., South Africa, and Japan/Brazil variants can spread more easily because they have certain mutations involving the surface spike protein on the virus that helps it attach to human cells.

The spike protein mutation "allowed these variants to emerge within populations" says DeSimone, adding that the variants are estimated to be between 20% and 50% more transmissible depending on the individual variant.

More Severe Illness

James M. Musser, MD, PhD, chair of the Department of Pathology and Genomic Medicine at Houston Methodist Hospital and Research Center, tells Verywell that the B.1.1.7 variant also causes more severe illness.

James M. Musser, MD, PhD

Vaccination is the best way to decrease the number of circulating COVID-19 variants that could be getting around.

— James M. Musser, MD, PhD

“A fair number of publications out of the United Kingdom show that it's a little bit more virulent than non-B.1.1.7 variants," says Musser, adding that the variant is responsible for between 55% and 60% of new cases of COVID in Houston and that the area has seen a higher rate of hospitalization in patients who contract it.

Genetic Clues

The spread of the B.1.1.7 variant has plateaued now, but in March, Musser and his colleagues published a preprint article outlining their work sequencing the genetics of variants of the virus.

After analyzing nearly 9,000 genome sequences of virus in patients from eight hospitals in January and February, the researchers determined that cases of the B.1.1.7 variant were doubling every seven days in the Houston area.

Do the COVID Vaccines Work Against Variants?

The number of people who are fully vaccinated against COVID continues to grow as eligibility to receive one of the three available vaccines (Pfizer-BioNTech, Moderna, and Johnson & Johnson) expands.

The Biden Administration has a goal to lift all restrictions on who can receive the vaccine on April 19. Several states, including Texas, have already expanded vaccine eligibility to any person over the age of 18.

Even with more shots in arms, the new variants are still a concern because some of them appear to be slightly more resistant to the vaccines. “We are keeping our eyes on these variants very closely and the type of disease that these variants cause,” says Musser.

DeSimone adds that “because these circulating SARS-CoV-2 variants contain mutations in the surface spike protein, its impact on vaccine efficacy is a concern.”

What the Evidence Shows

Current evidence suggests that both the Pfizer and Moderna vaccines are effective against the B.1.1.7 variant, but potentially less effective against the B.1.351 variant.

However, DeSimone points out that "the clinical significance of this impact is unknown" and that "the efficacy of the Johnson & Johnson COVID-19 vaccine varied by region in the study trials.”

Musser says that “vaccination is the best way to decrease the number of circulating COVID-19 variants that could be getting around. We need to get a lot larger percent of our population vaccinated.”

DeSimone agrees, saying that “vaccination and herd immunity will prevent outbreaks and control the spread of the virus in populations."

While we will likely keep seeing reports of new variants, DeSimone says that "with herd immunity, the risk of significant outbreaks should be extremely low.”

What This Means For You

Several variants of the virus that causes COVID-19 are spreading throughout the United States. Some of the variants are more transmissible than the original virus that circulated at the start of the pandemic, which is driving a surge of cases this spring.

The best thing you can do to protect yourself is to get vaccinated and continue to follow safety guidelines such as face mask-wearing, social distancing, and practicing frequent, proper hand hygiene.

3 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Centers for Disease Control and Prevention (CDC). US COVID-19 cases caused by variants.

  2. Centers for Disease Control and Prevention (CDC). About variants of the virus that causes COVID-19.

  3. Musser JM, Olsen RJ, Christensen PA, et al. Rapid, widespread, and preferential increase of SARS-CoV-2 B.1.1.7 variant in Houston, TX, revealed by 8,857 genome sequencesmedRxiv. Preprint posted online March 24, 2021. doi:10.1101/2021.03.16.21253753

By Valerie DeBenedette
Valerie DeBenedette has over 30 years' experience writing about health and medicine. She is the former managing editor of Drug Topics magazine.