The Oregon Health Authority released new modeling Friday showing a dramatically different coronavirus landscape than previously estimated, suggesting far more people already have been infected while simultaneously forecasting far fewer infections in the weeks ahead – even under worst-case projections.
Oregon’s estimates are the first to be released since Gov. Kate Brown allowed nearly all counties to reopen May 15 but the figures do not assess the full impact of those changes because not enough time has passed.
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The new projections indicate Oregon’s efforts to combat the novel virus have been extremely successful thus far.
“The results suggest that the epidemic is slowing in Oregon,” the 14-page report states, “but it is very sensitive to changes in policies, practices, and public adherence to community mitigation strategies.”
Most tellingly, the modeling suggests the coronavirus is spreading at levels low enough that it could be contained going forward. The all-important reproductive number – known as R naught – is forecast at or below one transmission per infection in two of three scenarios outlined by officials.
The modeling projects that about 20,200 Oregonians have been infected with coronavirus through May 22, with roughly 4,000 of those people identified.
That overall projection of 20,200 infections is not quite double the 12,000 that public health officials estimated in their last report on May 13. The substantial revision upward is based on conservative assumptions and data from the Centers from Disease Control and Prevention that fewer people with infections require hospitalizations.
“We continue to adjust the modeling to ensure that it tracks our ongoing understanding of the pandemic,” Dr. Dean Sidelinger, the state health officer and epidemiologist, said in response to written questions. “The changes to this week’s update allow a clearer picture and we’re confident in the accuracy of the model projections.”
Importantly, the new modeling forecasts far few infections in the weeks ahead under both best- and worst-case scenarios.
Assuming aggressive mitigation continued, infections through July 3 could increase by 1,200 for a total 21,400, according to the modeling. That’s a marked improvement of about 15 new infections daily instead of the current 55.
And even under the worst-case scenario outlined, cumulative infections could increase to 24,400 – 3,000 above the best-case estimate.
That’s a much rosier picture than previously forecast by the state.
Officials in their May 13 report estimated that infections could grow by 5,000 to 12,000 through mid-June, with the potential to hit 29,000 cumulatively.
“It continues to show that with aggressive interventions, we bend the curve downwards,” Sidelinger told The Oregonian/OregonLive. “As reopening becomes more widespread, we’ll be closely watching data and trends to make sure we are able to make smart policy recommendations to keep transmission low.”
The Oregon Health Authority, which creates the forecasts using software from the Institute for Disease Modeling, cautioned that forecast windows are wide and estimates should be interpreted with caution.
The coronavirus pandemic has thus far spared Oregon compared to many other states. While testing has identified infections in about 4,000 people and 151 people have died, Oregon has one of the lowest infection and death rates nationally.
State health officials wrote that the stay-at-home order issued by Gov. Kate Brown in March and other interventions have been effective at dramatically reducing infections.
The number of people requiring hospitalizations has also declined in recent weeks, the state noted, but “this trend may change as Oregon counties begin phased reopening.”
The health authority did not produce a modeling report last week, noting at the time that “experts want to allow a week to gather additional data on coronavirus infections following the state’s approval of 31 counties to begin limited reopening.”
Thirty-four counties have now reopened, with Washington County approved for Monday. Only Multnomah County has yet to apply.
But the latest modeling did not closely assess the impact of counties reopening.
“We could not yet assess the potential effects of reopening on hospitalization numbers because we only analyzed data through May 22nd, one week after reopening started,” officials wrote in the report. “Hospitalizations are assumed to typically follow new infections by about 12 days.”
New modeling will be released in two weeks, on June 12. That’ll be the first to incorporate changes from counties reopening.
That apparently will be after Brown considers whether counties can move into Phase 2 of reopening.
Sidelinger downplayed the significance of having modeling before such decisions are made, saying other data points are being watched.
“The phase recommendations are based on more specific datasets and their trends at the county level,” Sidelinger said. “The statewide modeling helps us see the overall trends in the state. As the phase one influenced data is incorporated, we’ll be watching this model for changes to the statewide trends.”
— Brad Schmidt; email@example.com; 503-294-7628; @_brad_schmidt
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