The County of Santa Clara Public Health Department provides an overview of SARS-CoV-2 virus concentration in wastewater samples collected at wastewater treatment facilities that serve people in Santa Clara County.
Protocol of Sample Collection & Testing: Samples for testing consist of “settled solids” from wastewater entering each treatment plant. Samples are collected 7 days a week from the wastewater treatment plants and are transported daily to a commercial lab for analysis. Laboratory staff process the samples to quantify pieces of the SARS-CoV-2 viral genome in the wastewater. These procedures use methods to concentrate solids and extract RNA and detect viral RNA. Results are typically ready within 24 hours of sample drop-off and are uploaded to this page. The quick turnaround and posting are one of the major advantages of utilizing this data.
Interpretation of Plots: Data reflected in the table below shows the results for one SARS-CoV-2 gene (N gene), and the concentrations are “normalized” by the concentration of a plant virus that is harmless to humans but is shed in stool (pepper mild mottle virus, or PMMoV). Normalizing by PMMoV adjusts for changes in the amount of feces in the sample and the efficiency of the procedures from day to day.
Wastewater typically contains waste from a variety of sources, such as from your shower or a commercial process. These types of waste do not have stool (which is the source of SARS-CoV-2) so they dilute the sample. Therefore, we adjust this sample to the known amount of feces in the wastewater to get an accurate result.
The curves displayed are the “7-day trimmed average” of the sample results. This is done by using 7 consecutive samples, eliminating the maximum and minimum among the 7 samples, and then taking the mean. The smoothing is right aligned. Trends in wastewater have been shown to track trends in COVID incidence.
This table is updated Monday, Wednesday, and Fridays.
