Idaho COVID-19 positivity rate up to 3.1%, rising in every county. Is it a concern?
Though COVID-19 numbers remain low, case metrics are again on the rise in Idaho.
The week of April 24, Idaho’s COVID-19 positivity rate rose to 3.1%, up from 2.5% the prior week. The week of March 20, it was 1.5%, according to state data.
Public health officials aim for a rate of 5% or less to indicate control of a respiratory pandemic. Idaho’s numbers remain below that threshold, but over the past two weeks, the positivity rate has increased in each of Idaho’s 44 counties.
“I don’t think it’s cause for alarm, but it is cause for us to pay attention,” Dr. David Pate, a member of the Governor’s Coronavirus Working Group, told the Idaho Statesman by phone.
He added that models indicate upward of half of all tests performed are at-home tests, which are not included in the state tally. That missing data skews the results.
Since the middle of March, the 7-day moving average of new cases has more than doubled across the nation, but Idaho has not seen that kind of surge.
Some of the increase is attributable to omicron sublineages, which have shown increasing transmissibility, Pate said.
BA.2, a sublineage of BA.1 — the variant known as omicron that caused Idaho’s surge in December and January — has been circulating in the state since at least late January. Now a third sublineage, BA.2.12.1, is rapidly outpacing even BA.2, indicating it may be even more transmissible, Pate said.
B.A.2.12.1 now makes up around 37% of new cases in the U.S., according to data from the Centers for Disease Control and Prevention.
At the end of April, the CDC’s director, Dr. Rochelle Walensky, said she did not expect the sublineage to cause more severe disease than other versions of omicron.
In early April, 100% of samples sequenced by the Idaho Department of Health and Welfare were omicron, but the data do not specify sublineages. Health and Welfare has not indicated that BA.2.12.1 has been found in an Idaho resident, but Pate said he thinks it is likely here.
Nearby states, such as Washington, are seeing large increases.
“That means we need to be watchful; we need to pay attention to what’s going on,” Pate said.
In April, Idaho’s deputy state epidemiologist, Dr. Kathryn Turner, said that widespread immunity in Idaho from vaccination or recent coronavirus infection would likely limit any bumps from BA.2 to levels below the surge seen over the winter.
Pate said he isn’t sure whether that’s the case, and pointed to data showing that various omicron sublineages appear able to evade antibodies from earlier infections, while also driving immune systems to create fewer antibodies than previous variants did. To Pate, this could leave many people vulnerable to reinfection.
“I don’t think we have a ‘wall of immunity,’” he said. “To the extent we do, it’s got big gaping holes in it.”
For now, Boise’s wastewater testing shows low amounts of the virus, though levels have risen in recent weeks. Idaho’s 7-day moving average incidence rate of new cases has gone from around 2.8 per 100,000 people to 5.1 per 100,000 as of Wednesday, according to state data. During the wave in January, it peaked at over 243.
Most Idaho counties remain in the CDC’s ‘low’ community risk category, while Adams, Washington and Payette are in the ‘medium’ category.
“We just need to be watchful,” Pate said.
