![Tracking infection dynamics in San Diego County. (A) Map showing the San Diego sewer mains (depicted in purple) that feed into the influent stream at the primary wastewater treatment plant (WWTP) at Point Loma. Overlaid are the cumulative cases recorded from the different zip codes in the county during the course of the study. The caseload was counted by cases per zip code from areas draining into the WWTP. The sizes of the circles are proportional to the diagnostic cases reported from each zone, and the color gradient shows the number of cases per 100,000 residents. (B) Daily new cases reported by the county of San Diego. (C) SARS-CoV-2 viral gene copies detected per liter of raw sewage determined from N1 Cq values corrected for PMMoV (pepper mild mottle virus) concentration. All viral concentration estimates were derived from the processing of two sample replicates and two PCR replicates for each sample (error bars show the standard deviations [SD]).](https://img.waterworld.com/files/base/ebm/ww/image/2021/03/16x9/F1.large.604f79b5248f3.png?auto=format,compress&fit=max&q=45&w=250&width=250 "Tracking infection dynamics in San Diego County. (A) Map showing the San Diego sewer mains (depicted in purple) that feed into the influent stream at the primary wastewater treatment plant (WWTP) at Point Loma. Overlaid are the cumulative cases recorded from the different zip codes in the county during the course of the study. The caseload was counted by cases per zip code from areas draining into the WWTP. The sizes of the circles are proportional to the diagnostic cases reported from each zone, and the color gradient shows the number of cases per 100,000 residents. (B) Daily new cases reported by the county of San Diego. (C) SARS-CoV-2 viral gene copies detected per liter of raw sewage determined from N1 Cq values corrected for PMMoV (pepper mild mottle virus) concentration. All viral concentration estimates were derived from the processing of two sample replicates and two PCR replicates for each sample (error bars show the standard deviations [SD]).")
Early in pandemic, UC San Diego postdoctoral researcher Smruthi Karthikeyan, PhD, collected local wastewater samples to predict COVID-19 outbreaks after she read that people with asymptomatic and symptomatic COVID-19 shed the virus in their stool.
Dr. Karthikeyan and her team sampled sewage water from July to November to see if they could detect the novel coronavirus. They discovered that they could, but the process was slow and labor-intensive, so they went on to develop a system for automated wastewater concentration using liquid-handling robots.
The research team compared the system to existing forecasting methods and found that it can predict COVID-19 cases in San Diego by a week with excellent accuracy, and three weeks with fair accuracy. They also found it is able to identify a single COVID-19 case in a building of about 500 people.
The system, which can process 24 samples every 40 minutes, extracts RNA from sewage samples and runs a polymerase chain reaction test to search for the novel coronavirus' signature genes. Dr. Karthikeyan then adds the data to a digital dashboard that tracks new COVID-19 cases.
The study's authors said the system is a faster, cheaper and more sensitive approach to wastewater surveillance.
