Every time someone flushes a toilet in Gilbert, it helps Arizona State University scientists track the spread of COVID-19 in town before it becomes an outbreak.
Since May, the town has been collecting weekly samples of wastewater from three locations – the Gilbert Commons lift station, which moves wastewater from a lower to higher elevation, and the Neely and Greenfield water reclamation plants.
It sends the samples to ASU’s Biodesign Institute for testing.
“When sampling first started, the COVID-19 restrictions were keeping COVID-19 wastewater concentrations so low they came back as ‘non-detect’,” said town Wastewater Manager Ken Snow.
“We eventually became concerned our testing locations were too diluted to get any reading at all. As restrictions were lifted we started getting detections, generally correlating with other reported metrics.”
Gilbert’s strategy captures almost the entire community, the only exception being a small area in northeast Gilbert, which flows to Mesa, Snow said.
Snow said the town general gets a “a snapshot of health” for northwest Gilbert discharging to the Neely Water Reclamation Facility, a separate reading on southeast Gilbert discharging to the Greenfield Water Reclamation Facility and one for the Gilbert Commons community, which discharges at the Gilbert Commons lift station before going to either of the two plants.
Snow said the town became involved with wastewater-based epidemiology – the study of community sewage for public-health information – after his counterpart in Tempe introduced him to the ASU researchers.
After nearly 1,000 residents died from opioid overdoses the year prior, Tempe in 2018 partnered with ASU on an anonymized monitoring system to detect the illegal drug and other substances in its wastewater for six neighborhoods.
This allowed Tempe to pinpoint where to send help for people to overcome their addiction.
Tempe had the world’s first public wastewater-based epidemiology dashboard that displayed opioid consumption broken down by neighborhood, according to professor Rolf Halden, director of the Biodesign Center for Environmental Health Engineering. His lab analyzes the sewage samples.
When COVID-19 hit the state earlier this year, Tempe and ASU decided to start measuring for bio markers of the novel coronavirus in the city’s sewer system.
“The world’s first COVID dashboard was launched by Tempe in May 2020,” Halden said.
The adjoining town of Guadalupe also signed on and its data is included on Tempe’s dashboard.
Halden said early testing of Guadalupe’s sewage found a cluster of infection, which prompted town leaders to embark on an education campaign that significantly reduced the virus levels in the community.
Halden said ASU also worked briefly with Peoria and is measuring the virus levels for Phoenix but that city is not publicizing its data.
The samples are taken at the 91s Avenue Wastewater Treatment Plant Facility in Tolleson. Phoenix operates the plant and co-owns it with Glendale, Mesa, Scottsdale and Tempe.
“The 91st Avenue plant is capturing the majority of pollutants in the Valley and that is exciting to get the data and try to help inform the public where we are in the state of the pandemic,” Halden said.
Genetic material from SARS-CoV-2 in people’s feces can signal infections shortly before clinical cases and deaths appear, according to scientists.
“The prolonged incubation time and virus shedding from asymptomatic infected cases have allowed the virus to spread quickly and to avoid medical detection and containment,” according to a published paper co-authored by Halden.
However, wastewater surveillance for RNA from the virus that causes the coronavirus is a developing field and is meant to complement – not replace – existing COVID-19 monitoring systems, according to the Centers for Disease Control and Prevention.
In Gilbert, 24-hour composite samples are collected with automated samplers three times a week by town workers at the three locations for a total of nine samples collected each week, according to Devin Bowes, a graduate research assistant with the Center for Environmental Health Engineering. She helps run the analytical tests for Gilbert.
Turnaround time for test results is relatively fast and is sent weekly to the town.
“Generally speaking, the sample is filtered, concentrated, RNA extracted and analyzed,” Bowes said. “Depending on the time of day the sample arrives, the process can take a day or two.
“Gilbert wastewater mirrors what we are seeing in Tempe wastewater, and on a larger scale, what we are seeing with known clinical samples throughout the Valley. We know that wastewater provides an early indicator of community infection, and we are working with Gilbert to integrate these data into pubic decision-making related to the pandemic.”
The town also is tracking its positive COVID-19 cases, using Arizona Department of Health Services data, which last week showed around 7,196 cases for Gilbert.
Snow said there are no direct costs for the town’s participation in the wastewater surveillance other than expenses for personal protective equipment, labor and incidentals.
Although it has its limitations, wastewater-based epidemiology surveillance of populations is shown to be cheaper and faster than medical screening for COVID-19 but cannot fully replace it, according Halden.
Halden said ASU has been doing wastewater monitoring for years but only gained media attention with Tempe’s opioid dashboard.
The university since 2001 has been analyzing urban wastewater from over 160 U.S. cities and other cities worldwide for harmful chemicals.
Halden said while everyone is focused on COVID-19 data, Tempe’s sewage surveillance shows a lot of health information can be learned from wastewater.
“Anything related to public health is detectable in wastewater,” he said.
According to Halden, a community can get a good look at the well-being of its populace by testing for levels of things such as pain killers, alcohol and illicit drugs. The beauty of the surveillance is the anonymity of individuals is maintained, he added.
Israel in 2013 was able to get a handle on a poliovirus outbreak that was detected through the monitoring of its sewage system by administering a vaccine. The country had a sewage-surveillance system in place since 1989.
The CDC in October announced it and other federal agencies are initiating the National Wastewater Surveillance System to get a better understanding of the extent of COVID-19 infections in communities. Nearly 80 percent of the country households are served by municipal sewage collection systems.
The federal health protection agency is currently developing a portal for state, tribal, local and territorial health departments to submit wastewater testing data into the national database for use in summarizing and interpreting data for public-health action.