COVID-19: SARS-CoV-2 Variants
Key messages
- Viruses, including SARS-CoV-2, naturally change or mutate over time resulting in new strains, or variants.
- The Omicron variant has a number of mutations occurring on its spike protein that make it more transmissible than previous variants.
- COVID-19 vaccines still offer protection against severe illness, hospitalization, and death from COVID-19, including circulating variants.
A variant is a new strain of the SARS-CoV-2 virus, the virus that causes COVID-19. Variants occur through mutations, which are changes in the genetic code of a virus. Variants have specific gene mutations that make them unique and different from the original virus. Viruses, including SARS-CoV-2, naturally change or mutate over time and new variants are expected to occur.
Public health surveillance
Variants are identified through a process called whole genome sequencing. Whole genome sequencing takes a sample of the virus from a positive SARS-CoV-2 test specimen and reads its genetic code. Genomic sequencing allows scientists to identify how virus samples from different people might have different genetic characteristics. This way, they can look out for new variants of the virus and better understand how different mutations change the characteristics of the virus, like how easily it spreads from person-to-person.
The Department of Health Services (DHS), the Wisconsin State Laboratory of Hygiene, and other laboratory partners regularly perform whole genome sequencing on a portion of positive tests. DHS has also requested that clinicians identify cases that may be good candidates for genome sequencing, such as individuals who have traveled internationally or individuals who may have tested positive after being up to date with COVID-19 vaccines.
See variant data from the Wisconsin State Laboratory of Hygiene.
Why do we track variants?
We track variants of SARS-CoV-2 to:
- Understand which strains are spreading in our state.
- Know which variants make up the largest proportion of new cases in Wisconsin.
- Help public health effectively plan COVID-19 prevention measures because some variants can spread more quickly than earlier strains and/or reduce the effectiveness of vaccines or treatments. The CDC (Centers for Disease Control and Prevention) classifies these as variants of concern.
- Understand how common the new strains are in our communities, not to have a real-time number of cases infected with each strain.
How are variants classified?
The CDC classifies variants into four categories:
- Variants Being Monitored
- Variants of Interest
- Variants of Concern
- Variants of High Consequence
A variant's classification is based on its attributes, including:
- How easily it spreads,
- How sick it makes people
- Whether COVID-19 treatments and vaccines can prevent it
The classification of a particular variant might change based on new research. Learn more about SARS-CoV-2 variant classifications on the CDC website.
Variants of Concern in Wisconsin
- Variant B.1.1.529, also known as the Omicron variant, was first discovered in South Africa in November 2021.
- On December 1, 2021, the United States detected its first case of the Omicron variant.
- On December 4, 2021, the Omicron variant was first detected in Wisconsin.
- On December 20, 2021, the CDC announced that the Omicron variant became the dominant strain among new COVID-19 cases.
- The Omicron variant continues to change into new sub-lineages. Sub-lineages are newer versions of the same variant. These sub-lineages differ based on mutations in the spike protein, but they still share a lot of the mutations as the original Omicron variant strain, B.1.1.529.
- CDC refers to Omicron variant sub-lineages as BA lineages.
- Attributes of the Omicron variant include:
- Potential increased transmissibility compared to the Delta variant
- Potential decrease in vaccine effectiveness against preventing SARS-CoV-2 infection compared to the Delta variant.
- Reduction in the effectiveness of some monoclonal antibody treatments
Visit the CDC website for more information on the Omicron variant.
- The Delta variant, B.1.617.2, was first discovered in India in October 2020.
- The Delta variant continues to change into new sub-lineages. Sub-lineages are newer versions of the same variant. These sub-lineages differ based on mutations in the spike protein, but they still share a lot of the mutations as the original Delta variant strain, B.1.617.2.
- CDC refers to Delta variant sub-lineages as AY lineages
- Attributes of the Delta variant:
- Increased transmissibility compared to the original strain of SARS-CoV-2
- Decrease in vaccine effectiveness against preventing SARS-CoV-2 infection compared to the original strain.
- Susceptible to monoclonal antibody treatments.
- Available evidence shows that the current COVID-19 vaccines are highly effective against severe illness, hospitalization, and death from the Delta variant.
Visit the CDC website for more information on the Delta variant.
Vaccines reduce a virus's ability to mutate
All viruses mutate, or change, over time. Mutation can happen very slowly or more quickly. The longer a virus sticks around, the more time it has to change. When a virus changes, it is called a variant. Many variants are no more harmful than the original virus, however, some can be more infectious or deadly. When our bodies are faced with a new variant, our immune responses built from vaccination or a previous infection may be able to fight it off.
Vaccines reduce a virus's ability to infect people. Vaccines still provide protection against current variants since many of the characteristics of the virus remain the same. The sooner people get vaccinated against COVID-19, the less opportunity we give the virus to keep mutating.
Get vaccinated
One of the most effective ways to protect yourself against severe illness, hospitalization, and death from COVID-19 is to get vaccinated. COVID-19 vaccines are safe, effective, free, and widely available.
