Healthy Central Valley Together Wastewater Data

Healthy Central Valley Together Wastewater Data

Healthy Central Valley Together (HCVT) is a partnership between public health departments, wastewater facilities, and researchers at the University of California campuses in Davis and Merced. We collect and use data on the levels of infectious pathogens in wastewater to inform public health action in the Central Valley.

Explore the pages below to see wastewater data from the region for respiratory, gastrointestinal and other pathogens.

Historical COVID-19 Data

We began testing wastewater for SARS-CoV-2, the virus that causes COVID-19, in November 2020 in Yolo County as part of our efforts to combat the COVID-19 pandemic. We expanded COVID-19 data collection in partnership with Merced and Stanislaus Counties in October 2021. We further extended our reach within these counties by engaging five additional cities in May 2022. Our partnership with WastewaterSCAN enabled us to expand data collection to a suite of pathogens including Influenza viruses, RSV, and norovirus from December 2022 through June 2024. In July 2024, WastewaterSCAN entered a new phase of wastewater-based disease surveillance, which includes extension of data collection through June 2025 for four of our partner cities (Davis, Merced, Turlock, and Woodland) in three counties. The graph below shows HCVT partners data for SARS-CoV-2 since December 2022.

About the Data

Healthy Central Valley Together partners with eight cities in three counties and WastewaterSCAN to monitor infectious diseases in the region. Together, we test wastewater for 6 respiratory viruses, 3 gastrointestinal pathogens, and 3 other pathogens. Samples of wastewater solids (the solid material that settles out of wastewater) are collected and analyzed two to three times per week by and for each community. Lab tests detect how many genetic markers of  each pathogen are detected in a gram of wastewater solids. We also measure genetic markers of a generally harmless virus called pepper mild mottle virus, or PMMoV, which is highly abundant in human sewage. We use PMMoV in the analysis as a process control to help correct for measurement-to-measurement variability. Dividing (or normalizing) the quantity of the pathogen’s genetic marker by the quantity of PMMoV’s genetic marker lets us compare results over time and from place to place.

You can learn more about WastewaterSCAN’s national program and further details about the data by visiting the WastewaterSCAN Dashboard.

Trends of the data through time indicate changes in the number of people in the community who are infected with the pathogen. Over time you will see this value rise and fall, indicating the rise and fall of the number of infections in the population served by each wastewater treatment plant.The results are reported to public health officials in Merced, Stanislaus and Yolo counties and to the public.

We display comparable data for each location in two ways: graphs and heat maps. The graphs show trends in our monitoring results for communities in each community monitored within three Central Valley counties. Dots indicate the results of each measurement. Trend lines show the 5-point trimmed average. We also combine data using a population-weighted average to show an average for each county, or an average of data for all HCVT partners together. On some graphs we also show three horizontal sections that indicate the lower, middle and upper third of all data collected by WastewaterSCAN across the nation over the past year. These sections help place the current levels of each pathogen in the Central Valley region within the context of wastewater-delivered infectious data across the United States.

The heat maps use color coding to show how many genetic markers were detected on each day a sample was tested. The darker the color on the heat map, the more copies of the genetic marker were detected (white spaces indicate days when samples were not taken). If you hover your cursor over a square, the actual data for that day will appear.