Historical COVID Data

Healthy Central Valley Together collects samples at least four times per week from each community’s wastewater treatment plant and analyzes the samples for SARS-CoV-2, the virus that causes COVID-19. Specifically, we measure the concentration of the N gene (N) of SARS-CoV-2, which is present in nearly all variants of the virus.

We also measure a generally harmless virus called pepper mild mottle virus or PMMoV, which is one of the most abundant viruses in human waste. We use PMMoV as an indicator of the “fecal strength” of each sample, which can change for different population sizes and factors like rain or water usage. Dividing (or normalizing) the SARS-CoV-2 concentration by PMMoV lets us compare results over time and from place to place.

The results reported as copies of SARS-CoV-2 per gram (gc/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 also indicate 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 COVID-19 clinical cases in the population served by wastewater treatment plants.

The Sewer Coronavirus Alert Network (SCAN), which initiated sampling at Davis and UC Davis in November 2020, continues to analyze those samples for Healthy Central Valley Together.