SALEM, Ore. – Oregon’s total confirmed coronvirus case count since the start of the pandemic surpassed 22,600 Friday as Malhuer County was sent back to Phase 1 and Gov. Kate Brown expanded mask requirements to office spaces.

The new face covering guidance requires masks in public and private office building hallways, bathrooms, elevators, lobbies, break rooms, and other common spaces, unless employees are at individual work spaces or in meeting rooms where six feet of distance from other people can be maintained.

The new requirement follows a list of COVID-19 safety restrictions and requirements implemented by the governor over the past two months. Health officials during the past two weeks have said these mandates have helped to slow the spread.

Daily cases of COVID-19 declined slightly during the week of Monday, Aug. 3, through Sunday, Aug. 9, according to the state’s weekly COVID-19 report. Hospitalizations have also plateaued.

“Seeing this decline is a sign that the spread (of COVID-19) may be slowing,” said Patrick Allen, director of the Oregon Health Authority.

The percentage of positive tests in the state also decreased to 5.4%.

But not everywhere in the state is seeing cases plateau.

Over the past two weeks, Malheur County, which borders Idaho in southeast Oregon, has had a test positivity rate of 26%.

Due to the rapid spread of the virus in the county, Brown announced that beginning August 17, Malheur County would move back from Phase 2 to Phase 1.

“Over the past month, COVID-19 cases in Malheur County have risen so much that restrictions must be put back in place or we risk further illnesses and death in the region,” said Brown. “I know this change is difficult, but immediate action is necessary in order to reduce the spread of the disease and protect all those who call Malheur County home.”

The county will remain in Phase 1 – where recreational sports, swimming pools, venues like movie theaters and arcades are closed – for at least 21 days.

On Friday, Malheur reported 18 new cases.

The total new cases reported in the state was 323 on Friday. There were two additional COVID-19 related deaths, increasing the state’s death toll to 385.

Also on Friday, the Oregon Health Authority epidemiologists released a study that indicates that the number of Oregonians who have been infected with the coronavirus may be 10 times higher than the reported rate of infections obtained through conventional testing.

The study, which was published in the Centers for Disease Control and Prevention’s Morbidity and Mortality Weekly Report, reported that as of mid-June 1% of Oregonians without COVID-19 had evidence of past infection of the virus in their blood.

“We suspected that a much larger segment of Oregon’s population has been exposed to and infected with COVID-19 than traditional diagnostic testing shows,” said Paul Cieslak, a study co-author and Oregon Health Authority medical director for communicable diseases and immunizations. “But these results also tell us that the great majority of Oregonians remain susceptible to this virus.”

The study found that nine of 897 blood specimens, collected from 19 health care facilities around Oregon between May 11 and June 15, contained antibodies against the virus that causes COVID-19.

In a statement by the Oregon Health Authority, officials said that seroprevalence surveys like this, where medical professionals test blood samples for antibodies, “may estimate the rate of infection more accurately than conventional testing.”

“Because most of us are still susceptible,” said Cieslak, “we need to keep practicing physical distancing and masking until we have effective vaccines, treatments or other means of mitigating illness.”