The Marion County Health and Human Services headquarters in Salem (Rachel Alexander/Salem Reporter)

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Marion County experienced a surge over the weekend in residents testing positive for COVID-19 that is concerning state and local health officials who can’t yet identify a cause.

Fifty-four county residents got a positive test back between Saturday, April 18 and Monday, April 20, the largest three-day increase since the first Marion County resident confirmed positive on March 8.

With 10 more people testing positive as of Tuesday morning, there are now 381 people confirmed to have COVID-19 in the county, a 20% increase. Fourteen have died.

Since the epidemic began, testing in the area has increased, but that doesn’t fully explain the spike. Over the weekend, 306 county residents got test results back. Eighteen percent were positive - a far higher rate than typical and three times the state average.

Statewide, about 5% of Oregonians tested for COVID-19 since late February have tested positive. In Marion County, it’s 11% since testing began.

“We are concerned. Additional research is being done to analyze demographics of positive cases, including whether the cases are sporadic or linked to a known outbreak, or household,” said Jonathan Modie, Oregon Health Authority spokesman, in an email.

There's been no equivalent increase in Polk County, which has 33 residents who have tested positive for the virus.

(Graphic by Rachel Alexander/Salem Reporter)

Marion County has consistently had the highest rate of people with COVID-19 in Oregon, despite testing at a rate similar to or lower than many other urban counties.

Modie said one explanation may be that Oregon’s Latino population has been hit harder by COVID-19. While Latinos make up about 13% of Oregon’s population, they account for 26% of the positive tests for COVID-19.

Marion County has a high Latino population, about 26% of residents, according to Census data.

Among the new cases, county health officials have not yet identified how many live or work in nursing homes, prisons or other facilities considered to be at high risk, though it appears known cases in facilities don’t explain the rise.

County spokeswoman Jolene Kelley said county officials planned to compile that information in the next few days. Most cases, she said, weren’t related to group living environments or facilities.

Most of those who recently tested positive have had contact with another infected person, Kelley said.

“Because Marion County continues to see new cases, we strongly encourage residents to adhere to social distancing guidelines which can be a powerful preventative tool when used consistently. And although wearing face coverings is not mandatory, we strongly encourage residents to wear masks when in public settings,” Kelley said in an email.

State data released Tuesday shows a slight increase in the number of Marion County nursing home residents confirmed to have COVID-19.

Six local nursing homes have outbreaks, defined as three or more residents or employees who have tested positive for COVID-19, or at least one death from the virus.

They are The Oaks at Sherwood Park in Keizer, Marquis Marian Estates in Sublimity, Country Meadows Village in Woodburn and Jason Lee Manor Apartments, Four Seasons Memory Care and Salem Transitional Care, all in Salem.

Together, those facilities have 46 people testing positive for COVID-19. But only five have been added in the past week, the state reports show. Facilities with no deaths and fewer than three people testing positive aren’t reported.

With four state prisons, a county jail and Oregon State Hospital within its boundaries, Marion County has more people living and working in institutions than many Oregon counties. But those facilities account for only a handful of the new cases.

To date, no Oregon State Hospital patient has tested positive for the virus, hospital spokeswoman Rebeka Gipson-King said. Nine have tested negative, and one has a test pending.

Three hospital employees have reported positive tests for COVID-19, Gipson-King said.

As of April 21, the Marion County Jail has not had any inmates test positive for the virus, said Sgt. Jeremy Landers, Marion County Sheriff’s Office spokesman.

Two of the four prisons in the Salem area have COVID-19 cases. At Santiam Correctional Institution, six employees and four inmates were confirmed to have COVID-19. At Oregon State Penitentiary, four employees tested positive for the virus.

No one at Oregon State Correctional Institution or Mill Creek Corrections Center has yet tested positive, according to Department of Corrections data.

Overall, Modie said the rate of new people getting sick with COVID-19 is falling across Oregon, despite some local spikes.

"We continue to flatten the statewide curve and estimate that Oregon’s aggressive physical distancing measures will continue to prevent new cases from rising above current daily levels of active coronavirus cases, as long as we maintain restrictions into May,” he said.

Contact reporter Rachel Alexander: [email protected] or 503-575-1241.