Central Valley Wastewater Data
Healthy Central Valley Together monitors wastewater for genetic markers of SARS-CoV-2, the virus that causes COVID-19. Lab tests detect if viral genetic material is present in samples analyzed three times a week. The results are reported to public health officials in Merced, Stanislaus and Yolo counties and to the public.
The results tell you how many markers of the virus were found in a gram of solid waste from a location. This data point also indicates how many people in the community served by a particular treatment plant have COVID-19. Over time you will see this value rise and fall, indicating more or fewer infections in the population served by each wastewater treatment plant.
We also measure a generally harmless virus called pepper mild mottle virus or PMMoV, which is a highly abundant virus in human waste. We use PMMoV in the laboratory as a process control to help correct for measurement-to-measurement variability. PMMoV can also serve as a measure of the “fecal strength” of each sample, which can change for factors like rain, water usage and industrial flow. Dividing (or normalizing) the quantity of virus genetic material by PMMoV lets us compare results over time and from place to place.
We display comparable data for each location two ways. This heat map uses color coding to show how many viral genetic markers were found on each day a sample was tested. The darker the color on the heat map, the more copies of the virus gene we test for were detected (white spaces indicate days when samples were not taken). If you hover your cursor over a colored square, the actual data for that day will appear. Below the heat map are charts showing trends in our monitoring results for communities in the three Central Valley counties we partner with once we use PMMoV to control for variability. White spaces indicate days when samples were not taken, and light blue spaces indicate days when there was no detection of virus genetic material in samples.
For the best experience in mobile, please view all charts in landscape mode.
In trend line charts, we display data that has been “smoothed” and “trimmed.” Each data point is a five-day average (smoothed) in which the highest and lowest result has been left out (trimmed). Because environmental samples like wastewater can fluctuate a great deal on a particular day, this average number allows us to see actual trends more easily. Historical data from prior to Dec. 1, 2022, is available here.