Essential data can be found in the most unexpected places, including the wastewater flowing freely through sewers.
During the early months of the Covid-19 pandemic, cities began tapping their wastewater to look for evidence of SARS-CoV-2, the virus that causes Covid-19. Now, more than a year into the pandemic, it’s clear that sewage surveillance carries several advantages over traditional surveillance.
Unlike individual testing, wastewater testing captures virus shed by symptomatic and asymptomatic people alike, and can test en masse the 80% of U.S. households connected to a sewer system. Such testing can detect exactly when dangerous viral variants enter a community and provide an early warning to public officials. It can even predict new outbreaks with a lead time of one to two weeks.
As a noninvasive, privacy-protecting method for disease surveillance, wastewater testing has helped overcome gaps in clinical testing for Covid-19 due to test kit shortages, false negatives, and the need for people to show up to get tested. To be clear, clinical testing is still needed for an individual’s medical care and contact tracing. But for public health management — meaning decisions that need to be made not just for one sick person but for an entire city or county — wastewater testing is the way to go.
Conveniently, wastewater samples are already being routinely collected and tested at more than 16,000 existing wastewater treatment plants. Surveillance for public health biomarkers essentially entails add-on tests for those samples. In other words, this approach is both pragmatic and scalable. It’s also a force multiplier: One test, costing from $300 to $1,200, can be used to monitor infections among hundreds, thousands, or millions of residents in a city, or to monitor the residents of a single dormitory, nursing home, or correctional facility.
At the University of Arizona, for example, routine wastewater testing alerted officials to new viral entry in a dorm during the first week of classes in the fall of 2020, which prompted officials to retest all 311 dorm residents and rapidly identify three emergent cases.
The pandemic has spurred the Centers for Disease Control and Prevention to partner with other federal agencies and states to develop a National Wastewater Surveillance System. As the CDC pilots this system in 31 states, three cities, and two territories, 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.
To ensure that the system that gets built is robust and flexible enough to identify a range of threats, my colleagues Xindi C. Hu and Marisa Henry and I formulated a three-pronged plan to launch surveillance in a cost-effective manner, as we discussed in a paper recently published in Environmental Health Perspectives:
- Deploy wastewater sampling at strategic sentinel sites, and scale sampling based on the pandemic phase, altering sampling as threat levels rise and fall.
- Identify or set up reliable testing labs near the sampling sites, since the testing marketplace is currently unstable, rapid turnaround is needed, and many labs do not include assays for public health biomarkers.
- Move wastewater testing from an academic enterprise to an operational policy tool through interagency coordination, workforce training, data sharing, and harmonized reporting tools.
Wastewater surveillance has 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 use cases of wastewater surveillance are manifold, and aren’t limited to chronic or infectious disease outbreaks. Researchers around the globe have developed protocols that enable communities to look to their sewers to estimate vaccine coverage, medication adherence, and even provide census measures. Targets of greatest interest to the CDC include antibiotic resistance, foodborne infections, and emerging infectious diseases.
A popular application among public health and public safety officials alike has been tracking illicit drug use: the types of drugs used in a region, how the mix concentrates or changes over time, and how amounts of drugs consumed fluctuate in response to new programs, policies, or actions.
Turning our attention to the opioid epidemic, several colleagues and I synthesized wastewater data with data from a local pharmacy, emergency medical services, and law enforcement from two Montana communities to identify unexpected drug threats, assess policing’s impact on community drug use, and quantify black-market activity. The European Monitoring Centre for Drugs and Drug Addiction has been using wastewater testing for more than a decade as part of a holistic monitoring system, and the Australian Criminal Intelligence Commission informs its operational priorities with wastewater data.
The emergence of wastewater surveillance as a public health and policy tool comes at an opportune time in the Biden administration’s infrastructure push. 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., and even the Republican counteroffer includes $35 billion for drinking water and wastewater infrastructure. Surveillance could easily be embedded into this plan.
Beyond replacing old pipes and dangerously outdated physical infrastructure, which received a D-plus rating on the 2021 infrastructure report card, funding from the American Jobs Plan could support development of sentinel warning plans in sewer systems across the country, along with the often overlooked translational research needed to determine how wastewater data can inform the work of public health and public safety officials.
Now is the time for the U.S. to capitalize on this free-flowing resource. As the weather warms and travel and tourism pick up, wastewater testing can tell officials if new viral variants begin to circulate. For communities like those in New Mexico and New England that have already vaccinated large swaths of their populations, wastewater testing provides a more reliable gauge than individual testing of when the virus has been truly eradicated.
By investing in this innovative data source now, government officials, school administrators, and business leaders can advance the technological know-how and public health predictive capabilities needed in the pandemic era and beyond.
Aparna Keshaviah is a senior biostatistician at Mathematica with expertise in wastewater surveillance and public health.