Oregon should brace for “exponential growth” in new coronavirus infections by the middle of July, according to the latest modeling released Friday by the Oregon Health Authority.
The new models were issued on the same day the state showed a near record-setting 250 new cases in a single day.
The grim forecast suggests Oregon could see anywhere from 910 new daily infections to an astounding 5,030 a day by July 16, depending on the level of spread.
Hospital admissions could hit 27 a day under the moderate scenario, a threshold that Oregon surpassed only once during the pandemic, a week after Gov. Kate Brown ordered residents to stay at home.
The pessimistic scenario suggests that admissions could reach 82 a day, a staggeringly high number that could challenge hospital systems across the state.
State health officials also modeled a third, optimistic scenario that would represent a slowdown in the pandemic’s spread. But they largely dismissed that as being implausible, given the state’s record level of identified infections this month.
Oregon’s nonoptimistic forecasts “demonstrate that increases in transmission, if maintained, would lead to exponential growth in new infections,” officials wrote.
The modeling is not a predictor of what will happen and instead is used for planning purposes. But the forecasts are calculated based on Oregon’s current trend lines, and the state’s pessimistic model from two weeks ago has appeared to be largely prescient.
That previous worst-case forecast, released June 12, indicated that Oregon could reach more than 1,000 new infections a day before the Fourth of July. Modeling indicates Oregon has identified only about one-fifth to one-quarter of actual infections, and identified infections from the past week have averaged more than 150 a day.
“It would be very difficult for us to contain with the same level of attention that we’d like to as we open up,” Dr. Dean Sidelinger, the state health officer and epidemiologist, previously said of 1,000 cases a day.
“So I hope that doesn’t happen.”
The modeling suggests coronavirus transmission has increased since Oregon’s governor allowed most counties to begin reopening May 15, but the degree of change was “informed by hospitalization and diagnoses data, not by the assumed effect of any policy,” state officials wrote.
The Oregon Health Authority ran the forecasts using software from the Institute for Disease Modeling. Officials assume about 4,000 Oregonians will be tested each day going forward.
The modeling appears to show that Oregon had recorded between 20,000 to 25,000 actual infections through June 18, with some number above 5,000 actually identified. (The report does not quantify each figure .)
Using the past as a baseline, officials projected what could happen in the weeks ahead. But they wrote that they faced some challenges, noting that infection levels are rising but so is the number of people tested.
“Our ability to accurately estimate how much transmission has changed recently is hindered by the limitations of data for both hospitalizations and diagnosed cases, as well as changes in testing practices,” they wrote.
Oregon’s most optimistic scenario could lead to new infections of about 180 a day, pushing the cumulative total since the start of the pandemic to 27,500 by July 16. It assumes the recent rise of infections this month has been the result of increased testing, not increased transmission, which officials deemed unlikely and implausible.
The moderate forecast suggests 910 new infections a day, reaching 38,300 cumulative infections by the middle of next month. It assumes Oregon’s recent spike in identified infections are due to increased testing and increased transmission.
The pessimistic forecast outlines 5,030 new infections a day, sending cumulative infections skyrocketing to 78,100 by mid-July — roughly tripling from the numbers as of June 18.
It assumes Oregon’s rising infection count was fully driven by increased transmission rather than more testing and increased contact tracing.
But the modeling does not take into account the recent order from the governor requiring residents to wear face masks in seven Oregon counties. Nor does it account for any other efforts that could be implemented in the coming weeks to slow the spread.
Officials found the modeling from two weeks ago so concerning that it was part of the reason Brown opted to pause Multnomah County’s reopening, although she eventually approved it.
Oregon so far has recorded few overall identified infections and deaths compared to other states across the country. As of Friday, the state had 7,818 confirmed or presumed infections and 202 deaths.
Oregon’s reproduction number — the number of new infections transmitted by one existing infection — is currently projected at about 1.23, according to independent figures that are not part of the state’s modeling but are referenced in the report. That’s the 12th highest nationally.
The state’s official modeling for the forecasts through July 16 assumed a reproductive number of 1.4 up to 2.