To get a clearer picture of how many people have the novel coronavirus in Baton Rouge and New Orleans, LSU and Tulane researchers are studying the cities' sewage systems.
The virus is detectable in fecal matter, so studying samples in wastewater systems could help map the virus' spread if a feared second wave of the virus strikes as Louisiana's economy reopens.
In Baton Rouge, testing has already garnered interesting results, according to LSU Civil and Environmental Engineering Professor John Pardue. He hopes the ongoing testing can be expanded into other parts of the state and become a key metric in Louisiana's response and mitigation efforts if a second wave of the virus surfaces.
"This isn't a new thing," says Pardue. "We're just building off something people have used in the past. Testing samples for coronavirus from sewer systems started in cities like Boston, Oregon and Houston first."
The data they've collected so far through the super-epidemiology method will be shared with local and state public health officials first before it is released to the public, Pardue said.
Along with LSU School of Veterinary Medicine Professor Gus Kousoulas and other university faculty, Pardue has spent the last few weeks testing samples collected from sub-basins near two sewage treatment plants in the south and north ends of the parish.
The testing involves taking wastewater samples, pasteurizing them and then extricating genetic information that shows traces of the virus.
Pardue says COVID-19 patients shed the virus in fecal matter and continue to shed the virus for up to five weeks after negative respiratory samples.
One single wastewater measurement can test an area of 300,000 people or an area that has 400 people living in it, he added.
"It's scalable and allows the researchers to know whether or not numbers are going up or down each day," he said.
Sewer samples can also be used to test for illegal drug use, various diseases and even dietary habits among residents in a community.
Rick Speer, director of environmental services for the city-parish, said he reached out to LSU and suggested a partnership to perform the specialized testing after reading about its use in other cities.
"We've been helping them by grabbing samples, which we do every day anyway for monitoring purposes," Speer said. "We split the samples with them, which we have been getting from our big treatment plants from two distinct areas in the city."
Speer said the city-parish plans to expand testing through the city-parish's wastewater system. By narrowing in on specific pump stations — the city-parish has more than 500 in various neighborhoods — they could concentrate data regarding the viruses infection rates even more.
Pardue and city-parish officials say a new pump station near LSU's campus and the surrounding area will help them track cases when students are scheduled to return in the fall.
"This is going to help us provide information to the state that they're not going to get even if they were going door-to-door," Pardue said. "They can have an overall picture of how prevalent the virus is in the community."
Researchers in New Orleans are also monitoring COVID-19 through wastewater samples. Samendra Sherchan, an environmental health microbiologist at Tulane University, is collecting raw sewage samples from wastewater treatment plants around the city and processing samples from other states.
The samples could act as an early warning system if New Orleans experiences a second wave. Early evidence from the Netherlands has shown that an uptick in virus appears in wastewater weeks before patients start presenting at hospitals.
Because both Baton Rouge and New Orleans are low-lying, flat cities, wastewater is collected at sub-basins before being directed toward large treatment plants. That offers an opportunity to monitor small communities like nursing homes, neighborhoods that were hard-hit by COVID in the spring and schools that may harbor asymptomatic carriers unaware that they are capable of spreading the disease.
“When students come back, all of them might not get tested,” said Sherchan. “We’re looking at alternative options to monitor wastewater from dorms and cafeterias.”
And with the start of hurricane season, floodwaters are also being considered for testing. While it is unlikely coronavirus, typically transmitted through particles in the air, can be transmitted via floodwaters cross-contaminated with sewage water, many other viruses are spread through floodwaters and researchers can’t yet rule it out.
“Coronavirus is usually not very persistent in the environment, but we need to do research to find that out,” said Sherchan. “No one has looked at floodwaters.”