Rather than looking at any one data point, we recommend monitoring trends over time. Our analysis suggests that the concentrations of pathogen genes are highly correlated to clinical incidence rates in the sewersheds. See publications listed here for more detail.

For more information about interpreting wastewater trends, see guidance from the CDC.

Verily tests wastewater for the concentrations of nucleic acids from many pathogens. The specific pathogens vary by program and may change over time. Please use the pathogen drop down menu to see which pathogens are tested at each site.

For all programs, Verily also tests samples for two controls: pepper mild mottle virus (PMMoV) for normalization (see What is PMMoV normalization?) and bovine coronavirus (BCoV), a virus that's added to each sample during testing as a process control.

The graph shows the copies of pathogen nucleic acid per unit of wastewater for a single collection site over time. You can select the pathogen and time period displayed. Points are measurements for a given sample and the lines show the same data smoothed to reduce day-to-day variability. To smooth, we take the five 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. However, as more data is added, the smoothed estimates for the most recent days will update and may appear to change.

If the target is not detected in the sample, the concentration is reported as 0 copies per unit. There may still be very low amounts of the target present that are below the detection limits of our procedure.

Results can be viewed in terms of how many copies of pathogen nucleic acid are present in a given quantity of wastewater. Depending on the program, Verily tests from the solid or liquid fraction of the sample. When testing from the solid fraction, this is reported as copies per dried gram of wastewater solids. When testing from the liquid fraction, this is reported as copies per liter of wastewater.

Alternatively, these measurements can be normalized by PMMoV (see What is PMMoV normalization?).

These measurements, raw and normalized by PMMoV, can be used as an indicator of how many people in a sewershed (the geographical area served by a particular treatment plant) have the virus. Over time you will see this value rise and fall, indicative of more or less clinical cases in the population served by wastewater treatment plants.

In addition to human pathogens, we also measure the nucleic acid concentration of pepper mild mottle virus (PMMoV), an extremely common, harmless plant virus found in food. By measuring the concentration of PMMoV in wastewater, we can account for 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 and between wastewater treatment plants.

When you toggle the display to show results normalized by PMMoV, the data will be reported as the ratio between the copies of pathogen nucleic acid per unit of wastewater and copies of PMMoV nucleic acid per unit multiplied by one million from a location. The units cancel in this ratio.

The heat map shows the quantity of pathogen nucleic acid copies per unit of wastewater for a single collection site over time. Samples are not collected every day, so on those days the map will show "no data". The heat map view can be helpful when reviewing results for pathogens that are rarely detected.