OSWEGO — Analyzing sewage for traces of the novel coronavirus has become a part of the largest public health response in memory, and local officials have adopted a testing strategy they say could identify outbreaks up to a week in advance of standard nasal swab testing.
Wastewater testing, which has been ongoing in the Port City throughout the summer, analyzes samples from treatment plants or other intakes along the larger wastewater system for genetic remnants of SARS-CoV-2, the virus that causes COVID-19. Local officials and experts in the field say wastewater testing can play an important role in an effective viral monitoring program, providing early detection and pinpointing geographic hot spots.
Hyatt Green, an assistant professor at SUNY College of Environmental Science and Forestry (ESF), helped pioneer the local wastewater monitoring program that he said has “now grown to be part of a really large New York state pilot program.” Green, whose lab developed a method for finding meaning in sludge, said the wastewater testing can offer a quick and efficient assessment of the viral presence in a particular sewer shed.
The city of Oswego started participating in that pilot program in June, and samples are now being taken from the city’s wastewater treatment plants and the SUNY Oswego campus.
Port City Mayor Billy Barlow said tracking the increase or decrease in COVID-19 levels in the community could be extremely beneficial, especially as the local economy attempts to return to normalcy. Barlow said Camden Group, the private firm that operates the city’s wastewater facilities, approached the city after learning a viral detection program was being developed at SUNY ESF.
Enrolling in the program was “a no-brainer,” Barlow said, and the city authorized the testing immediately and commenced June 3.
Each time a person infected with COVID-19 uses the bathroom, a small amount of the virus is excreted and enters the sewer or septic system, Green said. He and others are turning that usually unseemly process into real assistance for the public health response to the virus.
“What we're doing is capitalizing on the fact that the virus is excreted,” Green told The Palladium-Times. “We can take a sample and extract some of the viral nucleic acid out of it and see if the virus is there, and in some cases we can quantify how much virus is there.”
Green said scientists aren’t certain how SARS-CoV2 enters the gastrointestinal track, but there are high concentrations of the virus in individuals’ upper respiratory tract and saliva so it’s likely the virus is swallowed.
Barlow said wastewater from both the city’s treatment plants — one on the east side and another on the west side of the Oswego River — are sources for testing, and officials have the ability to trace samples to “just about everywhere in the city limits.”
“We can quite easily zone in to a two-to-four block area in a neighborhood to determine the origin of the virus,” Barlow said, describing the labyrinth of the city’s sewer system and the various pump stations and other collection points available for sampling.
Early detection of the virus is the most significant advantage of wastewater testing. Relying solely on nasal swab testing has several disadvantages, Green said, including a potential days-long turnaround for results and requiring an individual to physically present himself or herself to a clinician — something asymptomatic carriers are unlikely to do.
“Due to the fact that we’re detecting virus shed from potentially asymptomatic carriers, the viral RNA (ribonucleic acid) shows up in the wastewater before cases are detected in a particular area,” Green said. “We’re still working through the data, but it looks like we may have a three- to seven-day lead time compared to individual swab data.”
Earlier detection, even on the shorter three-day window, can provide a significant advantage in managing the potential spread in an area, according to public health officials. Oswego County Public Health Director Jiancheng Huang called the wastewater testing a worthwhile endeavor, and pointed to its success in other regions of the world. Huang said the potential to know several days in advance of an outbreak could be critical in helping public health officials respond.
“It’s a great monitoring tool,” Huang said, noting last week he signed a letter of support for a funding application for the project. “If you give me a week ahead of time we can be prepared. We can tell health care providers, get our staff organized and prepare for a surge in cases. There are so many things we can do if you give us a week’s time.
Another advantage of wastewater testing is it’s an efficient and cost-effective way to conduct widespread testing, and allows officials to indentify, and then prioritize, specific areas for public health response and management.
“So there’s both a temporal and spatial advantage,” Green said. “Based on wastewater results we may be able to prioritize certain areas or certain facilities based on the concentrations of viral RNA.”
Wastewater testing is an important component to the overall monitoring of viral activity, Barlow said, and is a “simple, cost effective way” to determine the extent or prevalence of COVID-19 in the community.
“The tracing should, in my opinion, comfort the public in knowing that the city of Oswego took the step to bring this testing here early on in the pandemic and its one more tool in our tool belt as we battle the virus,” the mayor said, adding Oswego was one of the first communities in central New York to start the wastewater testing.
The testing itself utilizes a machine called an ultracentrifuge, which Green described as something like a “very, very fast salad spinner” or vertical-style washing machine, that spins wastewater samples at extremely high speeds.
“What that does is pulls the viral RNA down to the bottom of the tube,” Green said. “From then on it’s basically just the same test as what’s done on a nasal swab. It turns out the difficult part is actually concentrating and purifying the small amounts of viral RNA that are there in the wastewater.”
Wastewater testing is now in high demand, Green said, and a large part of the analysis has been shifted to Syracuse-based Quadrant Biosciences, which is now analyzing dozens of samples each day from around the state.
Green said early in the pandemic samples were largely collected based on convenience, with wastewater being sampled at pump stations or at treatment plants that could easily be accessed. With the efficacy of wastewater testing now proven, Green said samples are being taken from areas and sources that could be most useful from an epidemiological perspective.
Testing locally was initially limited to the city’s two wastewater treatment plants, and later expanded to SUNY Oswego. Officials said the expansion to test more specific areas allows for more precise locating of potential outbreaks.
SUNY Oswego Associate Vice President for Facilities Services Mitch Fields said the school’s goal is to monitor viral intensity and produce a gross indicator of campus health. Tests that indicate the presence of the virus trigger additional tests further up the sanitary line to locate specific areas on campus, Fields said, and school officials can then concentrate health resources and behavioral interventions on those areas.
For testing done on the SUNY Oswego campus, samples are taken down to the dormitory level, providing officials with specific geographical locations of potential outbreaks — often in advance of infected individuals exhibiting symptoms.
Samples were initially taken from the college’s two sewage lift stations weekly, Fields said, but SUNY administration directed all campuses to start sampling and testing each residence hall twice weekly. SUNY Oswego started twice weekly testing of 12 residence halls and the two pump stations on Sept. 14, and officials plan to proceed with that frequency until directed otherwise.
Green said the frequency of testing is important in order to realize the benefits of wastewater testing, noting every day testing provides obvious advantages but in most cases is impractical.
“We’re recommending that sites be sampled at least two or three times a week,” Green said. “Sampling less than that is not going to allow wastewater surveillance to provide that early warning that we think it provides.”
Barlow said testing in the city had been done weekly at the start, but a twice-weekly model has now been adopted.
Barlow said the ability to monitor COVID-19 activity and its relation to events — such as holiday weekends, economic reopening and SUNY-related activities — is invaluable as the community moves to restart the local economy.
“It's important to use every tool we have in the toolbox and to understand the advantages and disadvantages of each tool that we have available, and to use all those tools in a coordinated fashion,” Green said. “We can use wastewater testing to tell us where we should do pooled saliva testing, and then follow up the pooled saliva testing with individual testing. So using all the tools we have in a coordinated fashion would probably allow us to use our limited resources much more efficiently.”