BACKGROUND:
The City of Sunnyvale Water Pollution Control Plant (Plant) has been participating in the SCAN (Sewer Coronavirus Alert Network) project that tests wastewater for COVID since November28, 2020 as part of a collaborative study led by Stanford, Santa Clara County Public Health, and the CDC. Wastewater SCAN is a national effort for monitoring COVID -19 and other infectious diseases through municipal wastewater systems to inform public health responses locally and nationally. Data from the SCAN project is reported to the CDC’s National Wastewater Surveillance System (NWWS) that coordinates and tracks the presence of SARS-CoV-2, the virus that causes COVID-19, in wastewater samples collected across the country.
SARS-CoV-2 is shed in feces by infected individuals even if they don’t have symptoms and can be measured in wastewater. More cases of COVID -19 in the community are associated with increased levels of SARS-CoV-2 in wastewater, meaning that data from wastewater analysis can be used as an early indicator of the level of transmission of COVID-19 in the community.
ANALYSIS
Wastewater samples are collected from the Plant daily by Stanford to measure the concentrations of SARS-CoV-2 and variants; the data is typically available in 24 hours. Data is analyzed in collaboration with Santa Clara County Public Health and CDC to provide epidemiological trends. A strong correlation has been established between concen trations of SARS-COV-2 RNA in wastewater and prevalence of COVID -19 in the community. 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.
Wastewater analysis measures the levels of non -infectious RNA (Ribonucleic Acid) in wastewater, not the viable virus. Results are reported as N and S gene concentrations expressed as copies per dry weight of wastewater solids. A plot of the concentrations of the N and S genes from SARS-CoV-2 in Sunnyvale wastewater solids since the beginning of the study in November 2020 is shown below. N and S gene s are in all SARS-CoV-2 variants , and their concentrations reflect the number of incident COVID- 19 cases in the sewershed . When evaluating the data, it is valuable to look at the overall trends, instead of measurements on any given day. Wastewater samples tend to have some variability simply due to the nature of environmental samples, but the general trends have proven consistent with clinical case trends.
Date: 10/14/2022
To: Sunnyvale City Council
From: Ramana Chinnakotla, Director of Environmental Services Subject: Update on Covid-19 prevalence in Sunnyvale Community RTC No: 22-0985 (Attachment 5)
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PLOT 1: COVID-19 Trends (N gene) since November 28, 2020 to October 12, 2022 in Sunnyvale Wastewater Samples
PLOT 2: COVID-19 Trends (S gene) since November 28, 2020 to October 12, 2022 in Sunnyvale Wastewater Samples
Notes: The blue lines on the graphs represents the N and S gene concentrations in copies per dry weight of solids normalized by using Pepper Mild Mottled Virus (PMMoV). The Y axis represents N and S gene concentrations in copies per dry weight of wastewater solids.
The last 6 months saw a rise in COVID-19 cases associated with the variants Omicron BA.2/BA.5 wave in t he Bay Area. Concentrations rose to peak in late May, and then remained relatively constant until about mid-July when they started to decline. SARS-CoV-2 levels measured from Sunnyvale’s wastewater sample s in the last six weeks indicate a slight increase around September 4, around the Labor Day holiday, and then a stable and declining trend. Omicron BA.5 variant remains the main circulating variant at present time. Since SARS- CoV-2 levels in wastewater data reflect the number of incident COVID- 19 cases in the community it can be deduced that number of COVID- 19 cases in the Sunnyvale community are low and on a declining trend. Data is available at all times to monitor trends and prevalence of COVID -19 in the community.
Additional information can be found at the following links:
1. wbe.stanford.edu
2. https://covid19.sccgov.org/dashboard-wastewater
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