FIGURE 1.

National estimates of biweekly proportions* of SARS-CoV-2 variants^† (A) and estimated normalized frequency of variant-attributed COVID-19 cases^§ (B) — United States, May 14, 2023–September 14, 2024

Abbreviations: NREVSS = National Respiratory and Enteric Virus Surveillance System; NS3 = National SARS-CoV-2 Strain Surveillance.

* Sequences are reported to CDC through NS3, contract laboratories, public health laboratories, and other U.S. institutions. Variant proportion estimation methods use a complex survey design and statistical weights to account for the probability that a specimen is sequenced. https://covid.cdc.gov/covid-data-tracker/#variant-proportions

^† Lineages reaching a prevalence of ≥1% with spike protein substitutions of potential therapeutic relevance and separated out on the COVID Data Tracker website (https://covid.cdc.gov/covid-data-tracker/#variant-proportions). Lineages were ordered by date of first appearance on the COVID Data Tracker. Lineages with identical spike residue 31 and receptor binding domain amino acid sequences (residues 332–527) were grouped with a representative lineage and denoted as “representative lineage-like.” “Other” represents aggregated lineages circulating at <1% prevalence nationally during all 2-week periods displayed.

^§ Normalized frequency of COVID-19 cases attributable to variants was estimated by multiplying biweekly counts of positive test results from NREVSS with variant proportions and scaling by the maximum NREVSS case count, which occurred in the 2-week period ending January 6, 2024.