Marion County has the highest documented COVID-19 rate in the state. No one is sure why.

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

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Marion County is posting the highest documented infection rate in the state for COVID-19 but authorities say they don’t have the kind of detailed information needed to determine why the area is a hotspot.

Health officials said they can’t point to any significant event or a single institution that seemed to be a COVID-19 factory.

Experts say with testing across Oregon remaining limited, it’s difficult to get an accurate picture of how widespread the virus is or whether the number of actual cases in counties is as varied as the data suggests.

Testing criteria in the U.S. are “changing rapidly and it’s not changing in an even way,” said Melissa Haendel, director of Translational Data Science at Oregon State University.

As of Friday morning, Marion County had reported 178 residents testing positive for COVID-19, 49 requiring hospitalization. That means 53 of every 100,000 residents have tested positive for the virus. The next highest rate in Oregon is Washington County, which has 39 confirmed cases per 100,000 people.

DATA: View Salem Reporter’s tally of COVID-19 cases, case rates and testing rates by county

Testing rates have varied widely by county, and Marion County is among those testing a higher percentage of residents. But that doesn’t fully account for the differences.

Multnomah County, which has reported fewer people ill with COVID-19, has more residents and is testing at a higher rate than Marion County. Other large Oregon counties with higher testing rates include Jackson and Linn.

“We’re still early enough in our curve in the outbreak that the total number of tests and positives are small enough per unit of geographical area,” said Dr. Dawn Mautner, senior health advisor to Oregon Health Authority. “It’s really hard to build a trend from the number of people that we have.”

Haendel has studied COVID-19 data from around the world and is part of a team of scientists and medical professionals running Flatten the Curve, a website with scientifically verified information about preventing the spread of the virus. She’s also coordinating a national effort to share data about COVID-19 patients.

She said health authorities can more effectively understand and stop the spread of disease in places where contacts of those infected can be traced and with follow-up testing. The virus doesn’t spread evenly between people – many cases elsewhere generally have been tied back to “superspreader events” where many people were together.

That would mean, for instance, if someone who tested positive attending a church service while contagious, health officials would identify and test everyone else at that service, not just close contacts like household members.

That’s a far cry from what most of the U.S., including Oregon, is doing. State guidelines for local health agencies from Oregon Health Authority say “resources should be focused on identifying household contacts of COVID-19 cases” and high-priority individuals like people living or working in long-term care facilities, essential workers and those at higher risk of serious illness.

Even when someone is a close contact of a confirmed case, they likely wouldn’t be tested unless they showed symptoms under current guidelines.

Haendel contrasted that with the successful approach taken in Singapore, where health workers attempted to identify and promptly test anyone who came in close contact of a confirmed patient.

Dr. Christopher Cirino, health officer for Marion County, said he couldn’t account for the higher number of cases here or identify a clear reason or event.

The county has identified some clusters of illness, often in households where multiple people got sick, he said. But there’s no one factor or location that otherwise stands out.

Tracing respiratory illness spread is difficult, he said, because it’s often not immediately clear where someone caught a virus. With a foodborne illness outbreak, it’s relatively easy to trace illnesses to a single restaurant or potluck, but few people can say where they caught a cold.

“It’s a lot harder to pinpoint the source. Who was that person who brought in the infection to a group?” Cirino said.

Local health agencies and the Health Authority have typically not released information about where people who have COVID-19 work or may have come into contact with the public, instead letting individual employers decide whether to share that information. 

In several Salem cases where people ill with COVID-19 worked for government agencies, that information has only been publicly shared after concerned employees contacted Salem Reporter or other local media.

Marion County has eight people working to investigate local patients and reach out to their contacts, with three more in training, county spokeswoman Jenna Wyatt said. With the outbreak ongoing, they prioritize identifying and checking in with close contacts, rather than more detailed analysis that could reveal larger patterns.

Wyatt wouldn’t say how many clusters county officials have identified or the general type of location, like a workplace or church, because of patient privacy. Asked how many local cases had contact with another confirmed case, she said the county doesn’t have enough staff to analyze the data they’ve collected right now.

Cirino said many cases now being reported are in people who likely caught the virus before widespread social distancing orders went into effect. He’s optimistic growth in the number of infected people in Marion County will begin to level off and then fall soon if people continue staying at home.

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

Rachel Alexander is Salem Reporter’s managing editor. She joined Salem Reporter when it was founded in 2018 and covers city news, education, nonprofits and a little bit of everything else. She’s been a journalist in Oregon and Washington for a decade. Outside of work, she’s a skater and board member with Salem’s Cherry City Roller Derby and can often be found with her nose buried in a book.