Verily Public Health

How do I interpret this data?

Rather than looking at one data point, we recommend monitoring trends over time. Our analysis suggests that the concentrations of the SARS-CoV-2 genes are highly correlated to COVID-19 incidence rates in the sewersheds [read the research].

How should I read these results?

Results may be filtered by location to view SARS-CoV-2 RNA occurrence in wastewater. Each location includes the SARS-CoV-2 copies per gram of dry solid waste and the copies per gram of the Omicron variant.

The data in the chart and graph have been smoothed, where measurements from nearby dates have been combined to reduce day-to-day variability and increase accuracy. Specifically, we take the 5 samples centered around a date and report the average after excluding the highest and lowest values. This processing minimizes the influence of outlier measurements and makes it easier to visualize trends in the data.

If the target is not detected in the sample, the concentration is reported as 0 c/g. There may still be very low amounts of the target present that are below the detection limits of our procedure. When a sample was not tested for a target, the concentration for that target is reported as “-”.

Read more about variability in wastewater data.

Please see the data dictionary for more information about each column shown in the table view.

What does “copies per gram” mean?

Results reported as copies of SARS-CoV-2 per gram (dry weight) of wastewater solids tells you how many copies of the SARS-CoV-2 virus were found in a gram of solid waste from a location. This data point can be used as an indicator of how many people in a sewershed (the geographical area served by a particular treatment plant) have COVID-19. Over time you will see this value rise and fall, indicative of more or less COVID-19 clinical cases in the population served by wastewater treatment plants.

What is PMMoV normalization?

In addition to the pathogens it tests for, WastewaterSCAN measures an extremely common, harmless plant virus that is consumed when people eat. It is called pepper mild mottle virus (or PMMoV). By measuring the concentration of PMMoV genetic markers per dry weight gram of wastewater solids, WastewaterSCAN can account for how much viral material is recovered from each sample and changes to the “fecal strength” of that sample. For example, heavy rain that drains into a wastewater system can dilute the strength of a particular day’s sample. This approach allows for comparison of results from day to day.

Our analysis suggests that both the concentrations of the SARS-CoV-2 genes measured as copies per gram of solid waste and those concentrations normalized by PMMoV are proportional to laboratory confirmed COVID-19 incidence rates in the sewersheds. Further, the relationship between these wastewater measures and COVID-19 incidence rates is consistent between the sewersheds in this study. That means a higher wastewater value at one plant compared to another suggests COVID-19 incidence rates are higher in that plants sewershed compared to the others.

References