By Melanie Padgett Powers, writer
Tracking wastewater for the SARS-CoV-2 virus can alert communities to the ups and downs of COVID-19 cases and potentially warn them about emerging virus mutations.
During the May 10 APHL 2021 Annual Conference session, “From Set-Up to Sequencing: Laboratory Adventures in SARS-CoV-2 Wastewater Surveillance,” public health officials explained how they have been using wastewater surveillance to better inform cities and towns about their local COVID-19 burden.
“Wastewater surveillance is the strategic sampling and testing of pathogens or other health targets in wastewater to better understand disease burden and spread within a community,” explained Mia Mattioli, PhD, EIT, MS, national wastewater surveillance science lead at the US Centers for Disease Control and Prevention (CDC).
One of the challenges of tracking COVID-19 has been the high proportion of asymptomatic and unreported cases. This “made the total community burden a relative black box for our surveillance,” Mattioli said. However, when it comes to wastewater, SARS-CoV-2 is shed in the feces of up to 80% of infected people, including those who are symptomatic.
“Wastewater data are also unique from case-based surveillance because they not only capture sub-clinical infections but are independent of healthcare-seeking behavior and testing access,” she said.
With that in mind, in September 2020, CDC launched the National Wastewater Surveillance System (NWSS). Wastewater surveillance is not a new idea—CDC has used it for decades to track polio, Mattioli said. However, it had never been done on a large scale, nor for a respiratory virus.
Research has shown that when wastewater surveillance detects increases in SARS-CoV-2 levels, that community sees a correlated increase of new cases just four to six days later.
Wyoming recruits communities
In 2020, when Wyoming started a wastewater testing program for SARS-CoV-2, public health officials recognized they needed to make it easy for small towns—which are often overburdened with responsibilities and small budgets—to participate.
The Wyoming Public Health Laboratory was first contacted by officials in Cody, a town with a population of 9,700, who wanted to try out such a program. The state laboratory jumped on board and started cold-calling cities and towns around the state to gauge interest.
To allay concerns of smaller towns, the laboratory connected with the Wyoming Association of Rural Water Systems, which reached out to communities to address their worries, explained Jim Mildenberger, emerging infectious disease supervisor at the Wyoming Public Health Laboratory.
The laboratory purchased auto samplers for the participating communities to ensure consistency of sample collection. The laboratory also paid for the samples and their shipping. Furthermore, if communities participated until the end of 2020, they were given a financial bonus.
“All they would literally have to do was be willing to take the samples, pack them up and send them to our public health lab,” Mildenberger said. “This we found to be a good way to reach out, especially to the small communities.”
The laboratory also tested the wastewater of facilities with high-risk populations, such as prisons and nursing homes.
The promise of wastewater testing
One of the most promising aspects of wastewater surveillance is variant tracking, Mattioli said. Currently, tracking is done by either targeting known mutations or by sequencing a specific genome region or doing a metagenomic sequencing of all nucleic acid within a sample.
Both approaches provide information on the presence of SARS-CoV-2 mutations, not on a variant itself. “However, by quantitatively monitoring multiple known mutations associated with variants, this can potentially provide information on trends in variant infections within a community, though researchers are still working to evaluate the performance of this approach,” Mattioli said.
Kara Nelson, PhD, who has been researching the presence of SARS-CoV-2 in wastewater since the beginning of the pandemic in the US, encouraged public health workers to get involved in wastewater treatment surveillance for SARS-CoV-2. Nelson is professor of civil and environmental engineering at the University of California-Berkeley.
Wastewater treatment surveillance “is an incredibly efficient way to confirm that cases remain low to support the continual reopening of society and to get an early warning if cases do start to increase—possibly where vaccination rates are lower, or due to the emergence of more contagious variants or should vaccine breakthrough occur,” Nelson said.
Melanie Padgett Powers is a freelance writer and editor specializing in health care and public health.
