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WSU researchers look for coronavirus clues in Spokane’s wastewater

UPDATED: Thu., June 18, 2020

Dave Moss, manager of the Spokane County Water Reclamation Facility, looks at the pressure readings large pipes carrying liquid sewage Monday, Jan. 6, 2014. Washington State University researchers believe these pipes might contain indications of COVID-19's spread in Spokane.   (JESSE TINSLEY)
Dave Moss, manager of the Spokane County Water Reclamation Facility, looks at the pressure readings large pipes carrying liquid sewage Monday, Jan. 6, 2014. Washington State University researchers believe these pipes might contain indications of COVID-19's spread in Spokane.  (JESSE TINSLEY)

How prevalent is the coronavirus in Hillyard compared to the South Hill?

The answer could be running in the pipes beneath our feet.

Researchers from Washington State University recently sampled wastewater from city pipes in three separate Spokane neighborhoods and are analyzing it for the novel coronavirus. It’s work they hope to continue and expand with government funding.

The results, the researchers say, could provide public health officials insight into which communities are most acutely impacted by COVID-19 and where resources – such as testing – should be directed.

The WSU scientists are not the first to look in wastewater for the presence of coronavirus, or to wade into the burgeoning field of sewage epidemiology. But their approach is unique, they say, because they’re not just sampling from a central treatment facility, as has been done in Coeur d’Alene and elsewhere.

Instead, the WSU researchers are trying to procure more localized data by pulling samples straight from neighborhood pipes. They’re not expecting to determine an exact percentage of residents in a neighborhood infected with the virus, but rather to spot spikes in infection early and assess an area’s viral load relative to other areas.

“We just need more ways of assessing where infections are and be able to do that at a more granular scale,” said Pablo Monsivais, an epidemiologist and associate professor at WSU.

The problem researchers are attempting to help address is that the coronavirus is incredibly infectious, but there remains an inadequate supply of tests to “really get on top of it,’ Monsivais said. According to public health officials, many people infected with the coronavirus may only ever develop mild symptoms or none at all, but could still pose a risk to others. And some particularly vulnerable communities may face barriers to health care, leaving them without access to testing.

The widely publicized testing data is just “the tip of the iceberg,” Monsivais said, “because of the lag in symptoms, the asymptomatic presentation of the disease and the fact that many people are undercovered and don’t have adequate health care.”

The research is being conducted through WSU’s Community Health and Spatial Epidemiology, or CHaSE, lab at the Elson S. Floyd College of Medicine.

In Utah, a six-week pilot program tested wastewater flowing into 40 treatment plants across the state and spotted a surge in the virus underground before test results above reflected the true spread of the disease, according to the Salt Lake Tribune.

Likewise, researchers at Yale University found samples taken from the treatment plant in New Haven, Conn., detected the high levels of the virus in wastewater about a week before case counts spiked there.

So how does Spokane get a sense of the prevalence of the virus, particularly in comparison from neighborhood to neighborhood?

Plucking samples of wastewater from city pipes may not be pretty, but it’s a more practical approach, under the circumstances, than going door-to-door and conducting nasal swab tests.

Research conducted around the world has demonstrated that people who are infected with the virus shed particles of it in their feces. All scientists need are the right tools to extract it.

The WSU researchers’ technique isn’t going to allow them to estimate the percentage of Spokanites who have contracted the virus.

It will, however, allow them to look at how prevalent the disease is in one part of the community compared to another.

“What we will be able to do is more accurately pinpoint what points of our community have higher burdens of infection,” Monsivais said.

The new research dovetails with work already undertaken by Monsivais and colleagues at WSU who developed a vulnerability index, which assessed the level of risk different communities in Spokane face from the coronavirus based on risk factors like population density, poverty and underlying health conditions.

With assistance from the city of Spokane, researchers recently took samples from three different Spokane neighborhoods.

The sites were selected based on Spokane Regional Health District data for the infection rate in a given ZIP code, cross referenced with WSU data on vulnerability to the virus.

The sites were intentionally selected to maximize contrast. One site, near Hillyard, was picked because known COVID-19 infection rates are high and the population is at high risk to COVID-19, according to the researchers’ vulnerability index.

The sample site on the South Hill was in an area determined to face less risk and fewer documented infections per capita.

Once at the site, researchers remove the manhole cover, take a plastic bottle with its top chopped off and lower it on wire into the wastewater below. They gather a sample of about 500 to 700 milliliters of less-than-potable water.

They chose a clear day to minimize the amount of stormwater runoff working its way through the pipes.

But a bottle full of sewer water isn’t of much use to anyone.

“Your first step involved getting it concentrated to where you can work with it,” said Douglas Call, a professor of molecular epidemiology at WSU and Monsivais’ partner on the project.

The goal was to find the corona needle in the sewer haystack as cheaply as possible. Luckily, it didn’t require ultra-fancy laboratory equipment – it turns out, all they needed was a fast centrifuge and polyethylene glycol, a common compound used in toothpastes and skin creams.

The polyethylene glycol, added to the centrifuge with the wastewater sample, “acts like a web,” Call said. It slowly pulls just the virus particles down to the bottom of the tube, where a pellet is formed.

The coronavirus is an RNA virus. For the researchers’ purposes, it must be translated to DNA with an enzyme and amplified for the genetic markers that distinguish the novel coronavirus through a process called polymerase chain reaction, or PCR.

The work is complicated by the fact that other detritus falls into the samples, interfering with the PCR. Humic acids, found in soils, are one culprit that can muddy the samples.

“Nothing’s ever perfect,” Call said.

The results, for now, are preliminary. The samples pulled from the Spokane sites were tested several ways, Call said. One showed “an unusually high signal” for the presence of the virus, but it has yet to be confirmed.

Any time a new system like this is set in place, there has to be validation testing and proper controls in place.

“Literally this morning, we just got the correct controls in the lab,” Call said Wednesday.

The first phase of the work was funded internally and only on a pilot basis. The team is now working to apply for a grant that would fund further research through the National Institutes of Health.

The regularity with which scientists can take samples and turn around results will largely depend on the funding they receive. A grant could provide salary support for staff members and increased testing.

“It’s actually not that expensive to do, but you still have to have money to do it,” Call said.

Right now, samples are tested at Call’s lab in Pullman. But with funding, they could be tested in Spokane, and results could be turned around the day after a sample is pulled from city pipes.

The city of Spokane has been eager to partner with the WSU team.

“It’s pretty exotic testing … extracting snippets of viral genetic material, then amplifying minute amounts with a polymerase chain reaction chemistry, from a wastewater soup of chemical and biological contaminants,” said Mike Coster, the city’s wastewater plant manager, in a statement to The Spokesman-Review.

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