SARS-CoV-2 Variant Proportions

To identify and track SARS-CoV-2 variants, CDC uses genomic surveillance. CDC's national genomic surveillance system collects SARS-CoV-2 specimens for sequencing through the National SARS-CoV-2 Strain Surveillance (NS3) program, as well as SARS-CoV-2 sequences generated by commercial or academic laboratories contracted by CDC and state or local public health laboratories. Viral genomic sequences are analyzed and classified as a particular variant. The proportions of variants in a population are estimated nationally, by HHS region, and by jurisdiction. The thousands of sequences analyzed every week through CDC’s national genomic sequencing and bioinformatics efforts fuel this comprehensive and population-based U.S. surveillance system established to identify and monitor the spread of variants.

These data appear on the CDC COVID Data Tracker at the following URL: <a href="https://covid.cdc.gov/covid-data-tracker/#variant-proportions">https://covid.cdc.gov/covid-data-tracker/#variant-proportions</a>

For more information on how these data are generated and used to provide estimates of variant proportions, please see the following references:

<ul>
<li>Paul P, France AM, Aoki Y, et al. Genomic Surveillance for SARS-CoV-2 Variants Circulating in the United States, December 2020–May 2021. MMWR Morb Mortal Wkly Rep 2021;70:846–850. DOI: <a href="http://dx.doi.org/10.15585/mmwr.mm7023a3">http://dx.doi.org/10.15585/mmwr.mm7023a3</a></li>
<li>Lambrou AS, Shirk P, Steele MK, et al. Genomic Surveillance for SARS-CoV-2 Variants: Predominance of the Delta (B.1.617.2) and Omicron (B.1.1.529) Variants — United States, June 2021–January 2022. MMWR Morb Mortal Wkly Rep 2022;71:206–211. DOI: <a href="http://dx.doi.org/10.15585/mmwr.mm7106a4">http://dx.doi.org/10.15585/mmwr.mm7106a4</a></li></ul>