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Mutations, Variants and Strains: A Coronavirus Guide


Viruses mutate to form new variants. It happens frequently, which is why the flu vaccine composition is reviewed each year and updated as needed. Like other viruses, the coronavirus (SARS-CoV-2) has mutated into different variants as well. This raises a lot of questions and understandably so. Here are answers to the most common questions we’ve heard at Lehigh Valley Health Network.

Why do viruses mutate?

When a virus enters your body, it infects one of your cells and tries to make copies of itself to infect other cells. In the process, the virus will occasionally make small errors called mutations. Depending on the mutation, the virus can become weaker or stronger. When the virus begins reproducing the mutation, it leads to new variants of the virus strain.

You might hear the terms variant and strain used interchangeably in the media, but the variant needs to have significant changes to be recognized as a new strain. For example, the strain identified in the United Kingdom (U.K.), B.1.1.7, has 17 genetic differences than the original strain of the coronavirus.

How are strains identified?

The nose swab PCR test is the most common and effective form of COVID-19 testing available. While the PCR swab test can detect if you are sick with COVID-19, it does not indicate which strain you are infected with. The Centers for Disease Control and Prevention (CDC) conducts random testing with sequencing to look for specific mutations. Since that level of testing is not done on a widespread level yet, it is very possible new strains of the virus may be more widespread than we realize.

Are vaccines effective against newly discovered strains of coronavirus?

The CDC says, “So far, studies suggest that antibodies generated through vaccination with currently authorized vaccines recognize these variants. This is being closely investigated, and more studies are underway.”

Public health officials will continue to study these strains to understand if they:

  • Spread more easily from person to person – Current data shows that the strain identified in the U.K. (B.1.1.7), the strain identified in South Africa (B.1.351), and the strain identified in Brazil (P.1) are more contagious than the original strain of the coronavirus (SARS-CoV-2).

  • Cause milder or more severe disease in people The newly discovered strains are not proving to cause more severe illness than the original strain. However, the original strain of COVID-19 can cause severe illness, especially for people with preexisting medical conditions.

  • Are detected by currently available viral tests Each of the new strains mentioned above can be detected on a PCR swab test.

  • Respond to medicines currently being used to treat people for COVID-19 – Data is still being collected on the effectiveness of medications and treatments that have been used to treat the original strain of the coronavirus.

  • Change the effectiveness of COVID-19 vaccines – Results of recent studies suggest that the vaccines available in the U.S. (Pfizer/BioNTech, Moderna and Johnson & Johnson) will provide some level of protection against the newly identified strains.

We are learning more every day about variants of the coronavirus. Check the CDC website regularly for updates about variants of the virus that causes COVID-19.

How do I know which strains are in my community?

You can check the CDC’s map titled U.S. COVID-19 cases caused by variants to see detected variants by state. However, it’s important to remember that not every PCR test is examined to determine which strain of coronavirus caused the person’s illness. Whether your community has a high level of spread from the original strain of the coronavirus (SARS-CoV-2) or a new strain, you should be cautious.

For more COVID-19 information, please visit LVHN.org/COVID19.