RAIN Incubator is a nonprofit leading some testing of sewage in the area, and the University of Washington is testing samples of raw wastewater weekly. The scientists are seeking to learn how to detect if concentrations of the virus may be spreading in the community, and also methodologies for this type of surveillance.
“A fair number of folks shed their feces and so sewers become essentially a great composite sample of the population,” said Scott Meschke, professor of environmental and occupational health sciences at the University of Washington. “So you can spend a whole lot of money going out and testing everybody individually if you want to see whether something is coming into the community, and you can do that all of the time. Or you can just take the kind of composite samples at a wastewater plant and get a picture of what’s coming into that population.”
In the testing of the sewers, scientists are trying to identify the genetic signal of the virus that causes COVID-19 through what’s called ribonucleic acid (RNA), which breaks down in the environment. “RNA doesn’t last very long outside of the host or body or cell,” David Hirschberg, founder of RAINIncubator, told the Seattle Times. “But in sewage, there’s enough fat in there or organic material that allows parts of it to exist without being degraded.”
Hirschberg said this type of surveillance is helpful because when you measure samples from the sewer, you are measuring everyone. “Sewage is away to unbiasedly test populations,” he said.
The research being done by the University of Washington is more about developing the methods that allow for this type of surveillance to be done efficiently than finding out what’s in the waste. But the methodology could lead to another tool to help control a virus such as the coronavirus.
“One thing we know is that the virus is not homogenously spread across the country; it’s in pockets here and there,” Meschke said. “So if you’re monitoring these small communities that haven’t had it introduced and you get an introduction, you can act early because you can usually detect it as much as a couple of days to a week early, before clinical science has shown up.”
At that point, the community could begin testing and contact tracing to help track and control the virus. “In a perfect world, what would happen is we’d be taking wastewater samples on, say, a biweekly or weekly basis.”
That’s the early warning piece and there’s also the potential to examine trends. “More people shedding [the virus] means more is present, so you can start to see whether it’s going up or down.” Meschke said. “It’s helpful because there’s so many people in the population who are asymptomatic but they’re still going to be contributing to the overall component sample.”
The University of Washington lab has done quite a bit of this type of research on the polio virus that’s been applied in national programs in Kenya and Pakistan. The methods are also used in other countries for work on typhoid fever.
“When talking about environmental surveillance, we’re almost always talking about sewage and so you can have this potential to all of a sudden surveil a whole lot of different things to understand how they’re moving in that type of population,” Meschke said.
