Researchers to track COVID-19 in sewage
Positive samples could point to hidden outbreak
A team of researchers at UW-Milwaukee and the Wisconsin State Laboratory of Hygiene has launched a program to monitor Wisconsin’s wastewater treatment plants for the virus that causes COVID-19.
Funded by a $1.25 million grant from the Wisconsin Department of Health Services, these researchers, in collaboration with the state Department of Natural Resources, will develop methods to monitor and detect COVID-19 infections in communities across the state at a scale not yet attempted elsewhere.
Studies have shown that people infected with COVID-19 can shed genetic material from the virus in their feces. The idea is that by detecting the virus in sewage systems, scientists could determine if an outbreak is occurring and how widespread the disease is in a community.
Sewage systems are designed to collect sewage from an entire population, giving researchers a “well-mixed” and centralized sample representing that population, said Sandra McLellan.
McLellan is a professor of human and ecosystem health at the UWM School of Freshwater Sciences and is leading the school’s efforts in the study. She says her team has already been able to detect
the virus, known as SARS-CoV-2, in wastewater samples from treatment plants in Milwaukee.
Experts believe this sewage surveillance will complement other tools used to monitor COVID-19, including testing testing individuals and tracking hospitalization numbers. But individual tests can be a “moving target,” McLellan said, and hospitalization rates capture infections that might have happened three weeks in the past.
Kayley Janssen and Dagmara Antkiewicz, researchers at the State Laboratory of Hygiene, said the team is hoping the wastewater results will be more timely. They want to eventually provide weekly updates.
“The more different looks we can get to try to better understand transmission, the more complete picture we can create about what’s actually the status of SARS-CoV-2 transmission,” said Jon Meiman, the state epidemiologist for environmental and occupational health at the Wisconsin Division of Public Health.
Monitoring wastewater for evidence of viral outbreaks is not a new concept: Israel began monitoring sewage for poliovirus in 1989. But SARS-CoV-2 is a new virus, and there is not a standard method for detecting it in wastewater samples, something that will have to happen if public health officials want to follow trends and compare results in different cities.
“The bottom line is that there is not a gold standard,” said Antkiewicz.
McLellan has already started collecting wastewater samples from treatment plants in Milwaukee, Green Bay and Racine.
The State Laboratory of Hygiene is working with the DNR, which oversees public water quality in the state, to recruit 80 treatment plants across the state, including plants in rural areas. Antkiewicz and Janssen anticipate testing wastewater samples from each plant each week.
How does it work?
When a person infected with SARSCoV-2 uses the bathroom, their feces — with genetic material from the virus — enters their city’s sewage system, along with the rest of the city’s flushed waste. This sewage flows to the local wastewater treatment plant; even people who don’t know they are infected essentially provide a test sample.
At the plant, workers collect wastewater samples before the water is treated and disinfected. The samples are sent to McLellan or the State Laboratory of Hygiene.
This is where things get tricky. In order to detect and quantify material from SARS-CoV-2, researchers have to extract and concentrate minuscule amounts of viral material. There are different ways to achieve this, but there’s not one set method and changing that method can change the final results.
The challenge is heightened in this case because in order to get data quickly, the State Laboratory of Hygiene needs to find a fast method of working with multiple samples at the same time. The team recently received $10,000 from the Wisconsin Alumni Research Foundation to develop an approach.
Once researchers have removed contaminants and concentrated the samples, they can detect and quantify the virus using the same methods used to test individuals for COVID-19.
Rolling this approach out across the state will take time.
“This is kind of a marathon, not a sprint, so we’ll get some data in a month, but we won’t really understand what that data means until we get the following month’s data,” said McLellan. “The longer we go with this, the better and more informative we expect this data to be.”
The State Laboratory of Hygiene has wastewater samples dating back from April and McLellan has samples that were collected in March. Once they have valid methods, the researchers will be able to see how COVID-19 transmission has changed since then and determine how their results map onto hospitalization and individual testing data.
Though the researchers are working with wastewater contaminated with SARS-CoV-2, they are not concerned about contracting COVID-19 from their samples.
“I am much more worried about going into the grocery store without a mask,” said McLellan. “You are much, much more likely to get a high exposure like that than from anything in the water.”
A new way of doing science
McLellan and the State Laboratory of Hygiene team are members of an international network of scientists working out how to use sewage to monitor COVID-19 infections.
Antkiewicz said that it’s “refreshing to see people so freely and openly sharing” details about their methods and equipment setups, and the scale and speed of the research is something she’s never seen in her field before.
McLellan also recently co-authored a grant request that brought in $250,000 from the Alfred P. Sloan Foundation to help form stronger communication networks among researchers and public health officials.
Though the immediate goal is to monitor the COVID-19 pandemic, these structures could help the next time a global health crisis arises.
“I’m sure there will be things that we would want to improve over time,” said Antkiewicz. “Hopefully tools like that ... will get us more ready for whatever next pandemic can come around.”