Omicron’s subvariant is in Oregon, but a push isn’t necessarily on the horizon
The omicron subvariant fueling COVID-19 outbreaks in Europe has been found in sewage from at least four Oregon communities, according to Oregon State University analyzes of sewage collected as part of the study. a statewide early warning system.
The early March results don’t guarantee an increase in cases, but they could underscore the potential benefits — and shortcomings — of a publicly funded sewage testing system touted as a way to reliably know the status of the pandemic in various corners of Oregon. .
Oregon health officials have contracted Oregon State University to analyze sewage samples from more than 40 sewage treatment plants across the state, providing officials with measurements of the amount of virus in a particular community and the most common variants of the virus.
The method has taken off locally and nationally, with federal health officials using sewage testing from around the country to track rising cases and an increase in the omicron BA.2 subvariant. But a state official involved in the project said the full benefits of the program have yet to be seen.
“This is all very emerging science,” said Dr. Melissa Sutton, the Oregon Health Authority‘s medical director for viral respiratory illnesses, who works with analysts at Oregon State University.
The main theoretical advantage behind sewage testing is that it can provide authorities and the public with advance notice of rising cases, faster than can be identified by traditional testing.
But it is not yet known exactly how long the program will provide. While an OSU searcher said the university produces test results twice a week, state health officials release the results on a public website once a week and with a one-week delay.
And, speaking on Tuesday, Sutton referred to data from samples taken during the week ending March 3. A spokeswoman for her agency cited delays in “collecting and delivering” the data, adding that more recent results would be available on Wednesday.
The nearly three-week-old OSU results do not show that the BA.2 variant, which is significantly more transmissible than the omicron variant, is prevalent in Oregon. But that could change, given that pandemic trends in Oregon have generally lagged the rest of the country by several weeks, Sutton said.
More recent data available at OSU reflected the same trends, with BA.2 appearing in some Oregon communities but not yet becoming dominant, said Tyler Radniecki, one of the university’s lead researchers for the program.
And so far sewage analyzes showed a steady decline or plateau in “viral concentration,” a measure of the amount of virus in a sample relative to the number of people using the sanitation system. This means that the analyzes reflect the rapid and continuous decline in the number of cases resulting from the tests.
On Tuesday, the average number of cases fell to 233 new cases reported per day, lower than at any time since July, before the delta wave.
If there is to be a surge, sewage testing should, in theory, show the upward trend before the official case count starts to climb. Although research results vary, Sutton said, the “viral concentration” in sewage samples can start to rise for up to seven days before the official case count begins to rise.
Some of the fundamentals of sewage monitoring for COVID-19 in Oregon have changed since it began in 2020. At the time, officials assumed there would come a time when there would be no no COVID-19 in Oregon, Sutton said. In this scenario, sewage monitoring would have served as an early warning of the return of the virus. Now the virus is everywhere. This means that the tests have a slightly different purpose – to identify cases of escalation and the prevalence of variants.
Sewage tests can provide an early warning of an impending surge, as people can shed the virus in their stool before they even know they are sick.
This means that within days of a person shedding the virus, a testing lab could theoretically identify that virus in sewage, said Dr. Ken Williamson, an expert with a Washington County company involved in the program. test of the OSU. By contrast, it can take up to two weeks between an infected person registering their illness in the official case tally, he said.
Radniecki, the OSU researcher, said sewage testing is immune to the biases involved in clinical testing and case monitoring. As for regular swab testing, the official case tally only captures people motivated to get tested for COVID-19 at a location that reports results to health officials. But wastewater analysis concerns everyone who uses a public sewage system.
“If you flush, you participate,” Radniecki said.
For Sutton, the sewage testing program appears to fit with the state’s new approach of leaving decisions about mask mandates and other protective measures to local jurisdictions. The results reflect the amount of virus found in a particular area — information that officials overseeing that area can use, Sutton said.
“Sewage can tell you when the virus is increasing in your community. It can tell you when potentially dangerous new variants are coming,” Sutton said. “It can allow you to act on it, to make those choices to add protection.”
Will there be a push?
Like much of the rest of the country, Oregon wonders if the BA.2 subvariant of omicron will bring a flood of cases to the state.
“I mean, I wouldn’t be surprised,” Sutton said, when asked if Oregonians should expect cases to increase in the coming weeks.
But Sutton added that existing immunity among Oregonians from vaccinations or infections during the recent omicron surge likely means it won’t be as bad as what Oregon has already seen.
It is clear that the presence of the BA.2 variant is growing nationwide. More than a third of COVID-19 cases last week in the United States were the BA.2 subvariant, according to the United States Centers for Disease Control and Prevention. In the region that includes Oregon, nearly four in 10 cases were likely of the BA.2 variant, according to agency estimates.
University of Washington COVID-19 forecaster Ali Mokdad agrees Oregon will likely be spared a BA.2 surge. Oregon’s cases will continue to decline through the summer, he predicted, with a potential spike in cases coming in the winter when immunity to vaccines and infections wanes.
Mokdad said Oregon and the United States as a whole face significantly different circumstances than Europe. In Oregon, many people have natural immunity to infections during the omicron wave, helping to protect large swaths of the population from the BA.2 subvariant.
“We are in a much better position than the Europeans,” Mokdad said.
The only variable that could change his projections is whether an omicron infection does not protect people against a BA.2 infection. But Mokdad said he hasn’t seen data that omicron doesn’t offer protection.
And yet, federal officials warn of the growth in cases. Dr. Anthony Fauci said Sunday that Americans should expect an increase in cases due to the subvariant, but not necessarily a massive increase.
Now is “not the time to declare victory,” Fauci said.
— Fedor Zarkhin