Health Department eyes statewide sewage testing


CODY — After a second round of sewage testing, the City of Cody was still COVID-19 free as of May 21, with negative results returning last Tuesday morning. Another sample taken the next day will come back in a few weeks.

“This is great news as counties around us continue to increase in their COVID-19 infection rates,” Park County Public Health announced Wednesday. “We believe these results are again a direct reflection of the hard work and commitment that Park County residents continue to demonstrate for themselves and their neighbors.”

Now, sewage collection efforts are being pushed statewide to paint a broader picture of the coronavirus in Wyoming.

Franz Fuchs, policy analyst for the Wyoming Department of Health, said the data collected isn’t so much about determining an exact number for the presence of SARS-CoV-2 in any given community,. Rather, it’s more for developing a trend line for the virus’ attack rate and its strength of location.

“You want to look at the samples as a trend,” Fuchs said. “Really trying to plot that over time.”

Park County has been teaming up with Massachusetts-based BioBot Analytics for the testing thus far.

Park County must pay BioBot $1,200 per test for the time being, a cost that will be reimbursed by federal CARES Act funding, but Fuchs said the WDH will have the same ability to test when it is ready to roll out its own sewage testing program starting in late June to early July. He said it will take about a month for the state to determine whether testing is a viable technique.

Fuchs said these tests will come at no cost to Wyoming communities besides possibly some labor hours required to perform the test locally, before results are sent off to the state lab. Smaller municipalities like Meeteetse, he said, might need to contract out this work to private firms that will provide their own testing sampler. He said the state is tentatively planning to provide individual communities $4,000 to buy this machine.

“Meeteetse would not probably be able to do this without help,” Fuchs said. “There’s a lot of hurdles to this especially for small places, and while we’re trying to make it as easy as possible, there may be some limits to this.”

Testing a community’s sewage for the presence of certain chemicals and bacteria is not a novel concept. That’s why Phillip Bowman, public works director for the City of Cody, said the municipality found it valuable to invest in the $9,544 Teledyne ISCO 6712C Compact Portable Sampler it purchased in April, in order to test for pollutants and other toxins into the future. The machine will also be reimbursed by CARES Act funding.

Fuchs said WDH already had most of the equipment it needed to perform the testing already on hand, and the largest cost will come from shipping samples to Cheyenne, a cost the state will also cover with CARES Act funds.

Fuchs said it would be ideal to have all participating communities testing twice a week.

Initially, he said Cody, Jackson, Laramie and Yellowstone National Park will be the first to participate. All four of these entities are already testing for COVID-19 on their own.

Neighboring communities will be able to borrow information statistically from the sewage testing, to draw conclusions about the virus’ presence in the regional community.

Fuchs said the testing will allow the state to make more educated, statewide health orders. It also serves as a much more cost-effective way of testing rather than trying to individually test thousands of people from a single community.

Once wastewater leaves a toilet, it enters the city’s sewer line. From this juncture, an automatic sampler machine collects a composite sample taken from the wastewater stream during a 12-24 hour cycle.

In Cody, a big motivation behind the testing is to see the virus’ presence before and after the tourist season.

Bowman said the most recent test performed on Wednesday revealed a 33% higher wastewater flow when compared to prior tests taken in mid-May and late April.

Once a sample is sent to the lab, a polymerase chain reaction test will be performed by using a PCR machine to determine the amount of viral RNA in a sample by a genomes per milliliter rate.

From that number, staff will refer back to the size of the community where the sample was taken to create a projection for the virus’ presence. This is determined by duplicating the RNA over around 40 cycles, and determining how many cycles it took for the virus to appear, if appearing at all.

Much like any testing involving the COVID-19 virus, sewage studies and test subjects have been too limited to make any scientific standards yet.

In a May 19 USA Today article, Newsha Ghaeli, president and co-founder of Biobot Analytics, said it is still not completely understood how much of the virus is shed in the stool by someone infected.

Further, Casey McGinley, a representative for BioBot, appears to have told Park County Public Health Officer Dr. Aaron Billin in an email there is “variability in detection rates” when virus concentrations make up less than 5% of a population base. In the City of Cody this means 500 or fewer cases.

Bowman said due to this testing ambiguity, it would be fair to say the COVID-19 sewage testing is perhaps more intended for a larger community.

And in larger sample pools it is much more effective. An April test in the Boston area reported 26-52% more cases of the virus than had been officially confirmed.

Also still less precise is what the minimum threshold of COVID-19 is needed from a community to register a presence in a lab setting, whether the virus’ presence varies from person to person in the stool, whether it degrades over time, and if a household’s proximity to the testing point affects recognition.

“The devil is in the details,” Fuchs said.

What is known is that feces excreted from COVID-19 infected individuals have shown a large presence for the virus, Fuchs said.

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