Wastewater Surveillance for SARS-CoV-2 in Bexar County, TX

Sewage samples are collected weekly from the San Antonio River Authority’s Salitrillo Wastewater Treatment Plant that services approximately 17,000 connections in Bexar County, TX. Samples are collected over a 24 hour period (representing a “composite”) on a weekly basis from the “headworks,” the location where all of the sewage enters the treatment plant. Samples are tested to detect and measure SARS‑CoV‑2, the virus that causes COVID‑19.

We measure the virus by detecting two genes specific to SARS‑CoV‑2, the N1 and N2 nucleocapsid genes, using RT-ddPCR. The N1 and N2 gene targets are measured and reported as a concentration, in number of gene copies per liter of wastewater.

We predict that changes in the concentration of SARS‑CoV‑2 in wastewater will reflect the community trends of circulating COVID‑19 infections. The daily number of newly reported COVID‑19 cases in Bexar County appear alongside the 7-day moving average of new cases. Changes in SARS‑CoV‑2 in wastewater may precede changes in reported cases because of lags in clinical testing.

Acknowledgements: We would like to acknowledge the San Antonio River Authority, the Health Collaborative and the City of San Antonio Metropolitan Health District for their support.

Contact: Kapoor Laboratory at UTSA – vikram.kapoor@utsa.edu