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Wastewater Analysis


This page provides regular updates on COVID prevalence based on analysis of wastewater data collected from more than 150 buildings on campus by Stanford’s Department of Civil & Environmental Engineering.

When reviewing the graph below, it is important to look at the overall, sustained trends, instead of measurements on any given day. Samples tend to have some variability simply due to the nature of environmental samples, but the general trends over time have proven accurate and consistent with trends in clinical cases.

The two blue lines on this graph represent the two genes (N, light blue and S, medium blue) that are present in every COVID variant, representing the total overall presence of COVID RNA in the sample. The orange and green lines track the prevalence of the variants Omicron BA.1 (green) and Omicron BA.2 (orange), the two dominant variants recently present.

Further information on how to read this plot is below.

Wastewater analysis is an increasingly important part of the university’s ongoing strategy to monitor the level of community transmission. SARS-CoV-2 (the virus that causes COVID-19) is shed in feces by infected individuals and can be measured in wastewater.

The university collects and analyzes samples from a large sewer main that drains wastewater from about 10,000 people studying, working and residing in the sewershed of Stanford’s Codiga Resource Recovery Center. The Codiga sewershed includes more than 150 buildings on campus (see map below), including faculty, staff and student housing, and classroom, research and office buildings.

Samples are typically collected six days a week and analyzed over the next 24-48 hours. Results are then uploaded to this dashboard.

Collection and analysis at the Stanford site began in July 2021. This effort is part of SCAN (sewer coronavirus alert network), a regional epidemiology project based at Stanford and developed in collaboration with local public health officers and 11 wastewater treatment plants in the Greater Bay Area and Central California, and the California Department of Public Health. Maps and wastewater measurements in those locations are available from SCAN.

Click image above to download map as PDF

SARS-CoV-2 Sewage Monitoring Data

Some information below is sourced from Santa Clara County Public Health.

More cases of COVID-19 in the community are associated with increased levels of SARS-CoV-2 genomes in wastewater, meaning that data from wastewater analysis can be used as an indicator of the level of transmission of COVID-19 in the community.

Wastewater analysis measures the levels of non-infectious RNA (Ribonucleic Acid) in wastewater, not the viable virus. There are no known cases of transmission resulting from exposure to wastewater.

Advantages of using wastewater to monitor COVID-19 infections

The use of wastewater to infer information about COVID-19 transmission has several potential advantages:  

  • Wastewater includes contributions from asymptomatic individuals and people who are unable or unwilling to obtain clinical tests, for a variety of reasons.
  • It provides a mechanism to monitor the level of community transmission as clinical testing declines, and other, more convenient testing takes place (such as home-based rapid antigen tests) that are not reported to the public health departments. Wastewater information is available sooner than information from clinical testing, which means that monitoring SARS-CoV-2 in wastewater can serve as an early indicator of increasing or decreasing COVID-19 infections in the community.
    • During an increase, this early information could be used to enhance public health messaging in our community to reinforce safe practices, promote more clinical testing, and highlight strategies our community can take to help stop a surge in new cases.
  • It can help confirm current trends of COVID-19 infections in our community that are based on clinical data.
  • It can increase confidence that clinical testing results are not biased by availability, time lags, and other factors.

SARS-CoV-2 Measurements in Wastewater

The plot shown above provides an overview of the results of SARS-CoV-2 measurements in wastewater over time. These are the results for two SARS-CoV-2 genes that are present in every variant: N gene and S gene. In addition, results for genes present in Omicron BA.1 (Del143-145) and Omicron BA.2 (LPPA24S) are shown. The concentrations for these genes are normalized by an internal standard (copies of RNA from the genome of pepper mild mottle virus, PMMoV).

Alternate data formats

Stanford University is committed to providing an online environment that is accessible to everyone, including individuals with disabilities. If you cannot access the content on this page, please contact to obtain the data in alternate formats.