Wastewater-based epidemiology (WBE) research by Arizona State University (ASU) researchers Olga Hart and Rolf Halden has revealed ways and means to identify dangerous pathogens in wastewater in near real-time.
Estimates based on European and North American data suggest that each person infected with SARS-CoV-2 will excrete millions if not billions of viral genomes into wastewater per day. Those estimates translate to between 0.15 and 141.5 million viral genomes per liter of wastewater generated.
The Hart-Halden study, by the ASU researchers, identifies what can and cannot be measured when tracking SARS-CoV-2 in wastewater. The work also highlights the economic advantages of the new approach over conventional disease testing and epidemiological surveillance. Therefore, the process can potentially identify levels of coronavirus infection at both a local and global scale.
“Our results show that exclusive reliance on testing of individuals is too slow, cost-prohibitive, and in most places, impractical, given our current testing capacity,” Halden says. “However, when preceded by a population-wide screening of wastewater, the task becomes less daunting and more manageable.”
Hart is the lead author of the new study. She has a Professional Engineer license in civil engineering, currently works for the Arizona Department of Water Resources in the groundwater modeling section, and plans to continue her researcher in the Biodesign Center for Health Engineering. Halden, who directs the center, is also a professor of engineering in the Fulton School of Sustainable Engineering and the Built Environment and author of the 2020 book “Environment.”
The technique boasts high sensitivity, with the potential to detect the signature of a single infected individual among 100 to 2 million persons. The process screens wastewater samples for the presence of nucleic acid fragments of the SARS-CoV-2 virus.
The WBE strategy involves first transcribing coronavirus RNA into complementary DNA (cDNA) by the reverse transcriptase enzyme, then amplifying the resultant DNA to improve signal detection. A sequencing technique confirms the viral presence in wastewater samples.
“We can monitor an entire community for presence of the new coronavirus,” Hart said. “However, trade-offs exist. To get the best results and avoid loss of information, we want to measure close to virus hotspots and take into account wastewater temperature and dilution when estimating the number of infected cases.”
In addition to reducing transmission and fatality resulting from SARS-CoV-2 infection, improved population-wide data provides other societal benefits. By pinpointing viral hotspots, researchers will be able to better direct resources to protect vulnerable populations through social distancing measures, while easing restrictions in virus-free regions, minimizing economic and social disruption.
Halden suggests that about 70 % of the U.S. population could be screened for SARS-CoV-2 through monitoring the country’s 15,014 wastewater treatment plants at an estimated cost for chemical reagents of $225,000.
More fine-grained surveillance could be achieved by using WBE to identify regional or global hotspots for the virus, then applying targeted testing of individuals using clinical methods.
Halden and his team created OneWaterOneHealth, a nonprofit project of the ASU Foundation that seeks to bring COVID-19 testing to those who currently cannot afford it.