Idaho's COVID-19 Positivity Rate Climbs as Ada County Stays at Highest Risk Level

COVID-19 indicators are moving upward in Idaho, according to the most recent state figures. For the week of June 22, the statewide test positivity rate reached 14.3%, nearly triple the 5% benchmark that public health experts use to signal better control of the virus. The previous week's rate was 12.1%, based on Idaho Department of Health and Welfare data.

Test results are reported with a one-week delay, and health officials have warned that the numbers probably understate the situation because so many people now test at home. Positivity has been trending upward since late March. Health and Welfare said in a Thursday tweet that cases are "increasing."

"We're clearly in another surge," said Dr. David Pate, a member of the governor's Coronavirus Working Group.

The June 22 data, released Thursday, arrived as much of the Boise area remained at the highest COVID-19 alert level set by the U.S. Centers for Disease Control and Prevention. At that level, the agency recommends universal indoor masking. Ada, Boise and Elmore counties were all in that category.

The latest CDC figures showed a mixed picture in Ada County. Its case rate fell from nearly 300 to 249 compared with the prior week, but hospital measures worsened. New COVID-19 admissions rose from 17 to 19.2 per 100,000 people, and the share of staffed inpatient beds occupied by COVID-19 patients increased from 6.6% to 8%. Canyon County, where the case rate stayed below Ada County's, was rated medium risk. At that level, the CDC suggests immunocompromised people speak with a health care provider about masking. Statewide, hospitalizations looked flat as of Monday, with 130 COVID-19 patients, seven of them in intensive care.

Regional CDC data covering Idaho, Oregon, Washington and Alaska point to omicron subvariants gaining ground. The BA.5 variant has been spreading quickly and accounts for 50% of cases in the region. Pate said Idaho either already has a high share of BA.5 cases or will within weeks. Some data hinted that the state's surge might already have peaked, but BA.2.12.1 was the dominant regional variant in May and June, and Pate described that as a concern.

He called BA.5 "the most transmissible of all" and said it also seems best able to evade immunity, so people infected this spring could be reinfected this summer. "We could see another blip as BA.5 now increases," he said, adding that Idaho might look as though it is leaving a surge just before another begins. Although other countries are further along in BA.5 surges, Pate cautioned that their experience does not translate easily to the United States, and that severe illness remains possible, particularly for unvaccinated people relying on natural immunity. "It's not over for the summer, I suspect," he said. "Things may get worse before they get better."

Pate also pointed to fusogenicity, the ability of a virus to cause cells in the lungs to merge. Ordinarily a virus must enter a cell, replicate, exit and infect another. Once cells fuse, he said, the virus can "move right through all the cells," doing significant damage, and antibodies act only when the virus is between cells.

Early omicron sublineages appeared less fusogenic than other strains, which led some to expect a milder disease. Research on BA.4 and BA.5, however, suggests their fusogenic potential has grown, which could translate into more severe infections. "This is not the same virus as the early omicron variants," Pate said. "It is different."