Test results from samples of untreated wastewater show a spike in SARS-CoV-2 in Oak Harbor and Coupeville since late August.

According to the Washington State Department of Health’s website, about 40% of people with COVID-19 — asymptomatic and symptomatic — release virus RNA in their feces.

The Wastewater-Based Epidemiology Program tests wastewater samples collected from treatment facilities across the state to detect the virus that causes COVID-19, SARS-CoV-2, and monitor infections in a community. The program is the result of a collaboration between the Centers for Disease Control and Prevention’s National Wastewater Surveillance System and the state Department of Health.

Since it’s hard to test every community member individually, the wastewater testing program has been helping authorities monitor infection trends in a population, providing information that is then combined with data on reported cases, hospitalizations and deaths.

Twice every week, the program tests wastewater from Oak Harbor and Coupeville. Thus far the program’s funding only allows for two sites to be tested in Island County, but Island County COVID Epidemiologist Jamie Hamilton wrote in an email that the county hopes to add Langley eventually. Hamilton leads the program in Island County.

Despite the fact that Oak Harbor and Coupeville samples seem to indicate that the county has one of the highest concentration levels statewide, this testing method is too recent to reliably indicate that higher concentration levels will mean more reported cases. Additionally, reported cases in South and Central Whidbey and Camano are higher than they are in Oak Harbor.

Hamilton wrote he hopes the county will one day be able to use the data to reliably measure infection rates.

“For now the concentration level is best understood as suggesting a general direction that the case rate is going,” he wrote.

Furthermore, sewer sheds are different in every community, so there isn’t a way to reliably compare them.

According to Hamilton, cases are likely rising as a result of the new variants, people’s behavior and waning immunity from past vaccines and infections.

“Our current swell doesn’t seem to have peaked yet,” he wrote. “I’ve seen some national modeling that predicts our current swell will crest this month, with the caveat that the West Coast has typically been behind the east in COVID-19 trends.”