SARS-CoV-2 Variant Proportions

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. Sequences contributed to CDC’s national genomic sequencing and bioinformatics efforts fuel this U.S. genomic surveillance system established to identify and monitor the spread of SARS-CoV-2 variants. These data appear on the CDC website at the following URL: cdc.gov/covid/php/variants/variants-and-genomic-surveillance.html For more information on how these data are generated and used to provide estimates of variant proportions, please see the following references: Paul P, France AM, Aoki Y, et al. Genomic Surveillance for SARS-CoV-2 Variants Circulating in the United States, December 2020–May 2021.