Wastewater monitoring shows prevalence of Omicron


Recent testing of Cottage Grove’s wastewater has shown that 98.3 percent of SARS-CoV-2 in the system is of the Omicron variant.

Oregon State University (OSU), in partnership with the Oregon Health Authority (OHA), has been testing cities throughout Oregon as part of a wastewater surveillance program since 2020, monitoring sewage for variants of SARS-CoV-2, the virus that causes COVID-19.

OHA announced the launch of the project in September that year and a $1.2 million grant, provided through the Centers for Disease Control (CDC), to fund the program for 30 months.

More than 40 communities, including the City of Cottage Grove, are participating in the statewide program, which covers more than 60 percent of Oregon’s population. The first positive test result in Cottage Grove’s wastewater came back in September 2020.

The monitoring program weekly collects and tests wastewater for traces of the coronavirus.

Wastewater monitoring for SARS-CoV-2 is an emerging science and was billed as an “early warning system” for COVID in a community. It allows for detection of the virus in a community before clinical cases appear and may detect COVID from cases without symptoms and those who do not seek testing.

Starting in early December 2021, researchers began testing for the Omicron variant, though positive tests in Cottage Grove reported only the presence of Delta for that month. Testing in February, however, has detected only the presence of Omicron.

According to OHA, when samples in wastewater test negative, it means the level of the virus is too low to be detected in the sample provided. That does not mean, however, the virus is not present in the community.

One possible benefit of wastewater sequencing is that it gives a broad picture of the what the virus is doing at community and state levels at a time when clinical samples are rare.

It is not currently possible to accurately detect the number of cases of COVID in a community based on wastewater data, however.

At the present time, test results in Cottage Grove show COVID is moderately present and has plateaued.

While the Omicron variant is on the decline across Oregon, there is an Omicron subvariant called BA.2 that OHA is monitoring closely through genetic sequencing and wastewater surveillance. Currently, just over 6 percent of all positive COVID-19 test samples are analyzed for sequencing, and within that analysis, BA.2 represents fewer than 1 percent of variants circulating in Oregon.

According to Lane County data on Feb. 28, ZIP code 97424 had reported 76 COVID cases in the past two weeks while ZIP code 97426 reported 28 cases.

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