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News >  Spokane

County by county, Washington epidemiologists track earliest symptoms of COVID-19

By Chad Sokol and Arielle Dreher The Spokesman-Review

State health officials and Gov. Jay Inslee are relying on myriad data points to determine when to lift the stay-home order or allow counties to proceed to the next phase of reopening the economy and society.

State Health Officer Dr. Kathy Lofy expressed optimism at several recent trends, including a decline in COVID-19 hospitalizations and a shrinking percentage of tests that come back positive each day.

New hospitalizations for COVID-19 peaked in late March and early April in Washington, with more than 550 residents hospitalized on March 22. Those numbers have since decreased. On Monday, 74 hospitals in the state were reporting a total of 390 patients with confirmed cases of the disease.

The number of tests administered statewide continues to increase, but fewer people are testing positive. About 7% of people tested each day are confirmed to have COVID-19. A month ago, 11% of tests were returning positive results.

Rates of positive tests still differ drastically by region, however, and Yakima and Benton counties are still experiencing peak-level rates of 19% and 15%, respectively.

In late March and early April, more than 400 new COVID-19 cases were reported each day. Now there are about 200 new cases per day – but that rate appears to be holding steady, which concerns Lofy.

“This is where the news isn’t quite as good,” she told reporters Tuesday. “This is data affected by the number of tests being done and who’s being tested. We started declining in April, but it looks like over the past three weeks, we’ve sort of leveled out around 200 people per day.”

Those numbersreflect case counts when the state is still under the governor’s “Stay Home, Stay Healthy” order. The ability to keep up with new cases will be important for the state’s contact tracing efforts going forward.

Epidemiologists also are tracking new cases by “date of illness onset” – that is, when patients with confirmed cases report they began experiencing symptoms of COVID-19.

The state Department of Health has begun releasing data sets showing how many COVID-19 patients said they began experiencing symptoms in each of the state’s 39 counties on a weekly basis.

Those data confirm that counties east of the Cascade Range generally have seen their peak numbers of patients beginning to experience symptoms later than those on the West Side. Franklin County, for example, reported 81 such patients in the week starting April 19 – more than any week prior.

Not all counties have seen a simple bell-shaped curve in their illness onset data. Benton County saw 95 patients beginning to experience symptoms in the week starting April 19 – a spike nearly as high as the county’s peak of 100 in the week starting March 22. Whatcom County had 22 patients beginning to experience symptoms in the week starting April 26, up from 10 the week before.

In Spokane County, the earliest reported symptoms of COVID-19 started the week of Feb. 16, according to the latest set of Health Department data.

Lofy said those numbers help show epidemiologists when transmission of the novel coronavirus likely occurred.

When investigating a confirmed case, epidemiologists typically ask the patient to recall when they began feeling symptoms. They also work to find out where the patient has been – and where they might have contracted the virus – during the previous two weeks.

With COVID-19, that process can be tricky because some people carry the virus without experiencing symptoms, and a person can be contagious before feeling sick.

The incubation period also varies. The Centers for Disease Control and Prevention estimates symptoms can appear in as little as two days or as long as two weeks after exposure to the virus.

“What we’re trying to do is understand how much transmission went on every single day,” Lofy said. “There’s an incubation period from when you get it to develop symptoms, but the illness onset date is the earliest date we have that’s closest to when the transmission occurred.”

Tracking the earliest signs of the illness, Lofy said, “helps us understand when the spread occurs and when spread is ongoing.”

Arielle Dreher's reporting for The Spokesman-Review is funded in part by Report for America and by members of the Spokane community. This story can be republished by other organizations for free under a Creative Commons license. For more information on this, please contact our newspaper’s managing editor.

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