Table 3.
CDC’s National Wastewater Surveillance System (NWSS) metrics for displaying SARS-CoV-2 concentration data to NWSS partners on the Data Collation and Integration for Public Health Event Response (DCIPHER) dashboard and to the public on the COVID Data Tracker webpagea.
Metric name | Description |
---|---|
15-day rolling detection proportionb | Proportion of samples from a site that had SARS-CoV-2 detected over the previous 15 days. SARS-CoV-2 is detected when concentrations are greater than the limit of detection, which is laboratory-specific. |
Percent changeb | Linear change in SARS-CoV-2 concentrations from a site over time (the previous 8 or 15 days) or for a given number of samples (the previous 3 or 5 samples), calculated from the slope of a log-normal linear regression line. |
Trendsc | SARS-CoV-2 concentrations for a site categorized as sustained decrease, decrease, plateau, increase, or sustained increase. Categorizations are determined from the direction and statistical significance of the slope of the “Percent total change” metric regression line. Sustained trends (sustained increase or sustained decrease) are based on the 5 most recent samples. If a significant sustained trend is not found, shorter term trends (increase or decrease) are evaluated based on the 3 most recent samples. If no statistically significant trend is found, the trend is classified as plateau. |
Percentilesb | Quintiles to compare normalized SARS-CoV-2 wastewater concentrations for a site’s most recent sample to historic samples for that site. |
Displayed on both the DCIPHER dashboard and COVID Data Tracker.
Displayed on the DCIPHER dashboard only.