Methods & Data Sources

NWGSGrid ingests wastewater viral concentration data from state and local partners and national programs, including the CDC National Wastewater Surveillance System (NWSS). Viral concentrations are normalized and converted into wastewater viral activity levels (WVAL) that can be compared across time and space, similar to the categories used in existing federal dashboards.

Normalization accounts for variations in flow rate, population served, and laboratory methods to enable meaningful comparisons between sites and over time.

Genomic analyses leverage sequences and metadata shared via GISAID and other repositories. Variant calling and lineage assignment follow established pipelines (Pangolin, Nextclade) to classify sequences into WHO-designated lineages.

In line with GISAID's access agreements and sharing policy, NWGSGrid presents derived results only—such as variant prevalence, spike mutation frequencies, and EPI_SET identifiers—without redistributing underlying raw sequences. This approach ensures compliance with data-sharing principles while providing actionable genomic intelligence.

Protein structure visualizations are built on experimentally determined and computed structures from the Protein Data Bank (PDB). Interactive exploration uses modern web-based viewers such as Mol* for visualization of spike and other viral proteins.

When mutations are highlighted on structures, their positions are mapped to reference structure coordinates. Note that some structures may not include all protein regions; flexible regions or those not resolved in experiments may not be visible.

Clinical burden and demographic context are derived from public health surveillance systems and population datasets, including:

• State health department reports and hospitalization data • CDC respiratory illness surveillance systems • U.S. Census Bureau and American Community Survey (ACS) population estimates • HHS hospitalization and healthcare capacity data

Data are aggregated to appropriate geographic and temporal levels to protect privacy while enabling meaningful analysis of burden and equity across demographic groups.