A new study from UC San Diego demonstrates that wastewater surveillance can detect Covid-19 in a single infected, asymptomatic person living or working in a multi-unit dwelling such as a university campus building. Wastewater surveillance can detect a case up to 3 to 4 days before individual testing can. Early detection means that those infected can quickly isolate and if necessary receive treatment, preventing rapid spread of the virus.
Wastewater surveillance is an underused yet cost-effective, non-invasive mass testing strategy that can detect virus shed by symptomatic and asymptomatic people alike. Highly localized wastewater surveillance provides an alternative to contact tracing, an intervention that has been difficult to implement in many countries. With a small enough group, testing everyone potentially exposed is justified and usually acceptable. With highly vulnerable, unvaccinated children returning to classrooms wastewater surveillance could be a valuable tool in keeping them safe.
People infected with SARS-CoV-2, Covid-19, are known to shed in their stool and urine, even if they aren’t experiencing any symptoms. Unlike individual testing, wastewater surveillance paints a broader picture, detecting exactly when new viral variants enter a community, providing valuable data and an early warning to public officials. Time is one of the most valuable modalities of infectious disease control. Wastewater testing can predict new outbreaks with a lead time of one to two weeks. This surveillance can and should be used with other interventions to facilitate a safe return to university campuses, schools, and workplaces.
The study released by the University of California San Diego School of Medicine was conducted on campus. Researchers used a large-scale geographic information systems to build a wastewater monitoring system that was associated with the on-campus residences of 7,614 individuals. Wastewater surveillance led to the early diagnosis of nearly 85% of all Covid-19 cases on campus. Covid-19 testing rates increased by 1.9 to 13 following wastewater notifications.
A team of students and staff were deployed each morning to collect sewage samples from 126 collection robots set up to monitor 350 buildings. Each auto-sampler collects wastewater into a pre-labeled sample bottle. Both the auto-sampler and the sample bottle are associated with a unique barcode . The result for each sample is uniquely identified by time and place.
When the researchers receive the samples they process the sewage using a different kind of robot, one that concentrates the virus using magnetic nanoparticles, and extracts RNA—the genetic material that makes up the genomes of viruses like SARS-CoV-2—from the samples. Polymerase chain reaction (PCR) testing is used to detect the virus’ signature genes. If the sequencing reveals all three viral genes tested, the sample is considered to be positive.
The system is part of the University’s Return to Learn program, which aims to allow for safe in-person teaching and research. The program has three pillars; risk mitigation, viral detection and intervention which includes other policies like mask-wearing, symptomatic and asymptomatic testing, and case isolation. All of these policies complement wastewater surveillance providing layers of protection and the strongest possible defense against Covid-19. The success of the Return to Learn should be an adopted not just by colleges, but schools, workplaces, and other congregate living situations such as nursing homes and prisons.
Wastewater surveillance is not a new concept. Wastewater testing provided an early warning for outbreaks of hepatitis A and norovirus in Sweden and helped eradicate polio in Israel and India. As early as the 1930s, U.S. researchers recognized that the very same markers of disease that clinicians look for in stool samples could be measured in wastewater to track disease in entire populations.
The Covid-19 pandemic has prompted the CDC to partner with other federal agencies and states to develop a National Wastewater Surveillance System. The system is currently being piloted this system in 31 states, three cities, and two territories and the Department of Homeland Security and the National Institute of Standards and Technology are leading efforts to identify standards for wastewater sampling, testing, analysis, and reporting to public health officials. Under the American Jobs Plan, the Biden administration has allocated $56 billion in grants and low-cost loans to upgrade and modernize drinking water, wastewater, and stormwater systems in the U.S.
If the infrastructure push succeeds, we will be well placed to invest in a permanent, national wastewater-based epidemiology network that could prove vital in preparing for faster and more effective control of this and future pandemics. The network could trace other stool-borne pathogens, including influenza while also revealing health disparities and vulnerabilities among communities by monitoring for biomarkers of noncontagious diseases, all key challenges to tackle in the coming years.