Aggressive social distancing restrictions have helped Oregon avert thousands of new cases of coronavirus and hundreds of additional hospitalizations and should continue for at least six more weeks to prevent a resurgence of the epidemic, according to the latest estimates.

New projections released Saturday by the Oregon Health Authority show the state has avoided 18,000 new cases of the highly contagious virus and as many as 500 hospitalizations since strict social distancing measures were imposed last month. The figures are just estimates but ones public health officials pay close attention to.

The Institute for Disease Modeling found that aggressive measures have essentially reversed the course of growth of the epidemic and that without them, the state’s hospital systems would have likely become overwhelmed by late April.

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“The measures are working and we know people need to continue those measures at least through the middle of May," said Dr. Dean Sidelinger, the state health officer and epidemiologist.

The efforts have led to a plateau of new coronavirus cases in Oregon, though the state isn’t expected to see a drop-off in numbers for at least six weeks, according to the Bellevue, Washington-based research center that is part of the Global Good Fund, a collaboration that involves Bill and Melinda Gates.

“Oregon’s recent donation of ventilators to New York is a strong testament to the success of its early and forceful control measures,” the authors wrote.

They also estimate that Oregon has 7,000 infections, vastly more than the 1,447 that have been identified through testing. The report says Oregon likely saw its first case of the virus before February, earlier than previously thought.

Latest estimates show social distancing, sheltering at home are reducing course of the coronavirus in Oregon

The authors warned against relaxing the restrictions, saying such a move is “likely to result in epidemic resurgence.”

They stressed the “urgent need for enormously increased testing capacity" before the state considers easing social distancing efforts. They added that Oregon officials must also conduct detailed contact tracing, test asymptomatic at-risk people and quarantine those who are infected.

“It will not be possible to relax social distancing measures and avoid an epidemic rebound without significantly increased testing," the report says.

Sidelinger said he is encouraged by the latest estimates, which “show the aggressive social distancing measures in place and the sacrifices people are making to follow those are having an impact in Oregon.”

The report estimates that current case numbers have been reduced by 55 percent to 75 percent compared to what they would have been without such steps.

He said the modeling shows new cases are rising at a “very slow pace” and are projected to level off over the next six weeks when they’ll start to drop.

“Our peak is more of a plateau than a pointy peak,” he said.

Sidelinger acknowledged the toll that restrictions have taken on Oregonians personally and economically.

He said spring weather is hard to resist but urged residents to continue to stay home beyond essential trips.

“Oregonians really crave those early spring days and we are hoping that they can delay some of that gratification -- maybe enjoy it from an open window, their balcony, front porch or backyard and do it in a way where they are distant from their community," he said.

“Wait until summer,” he advised, “to really go out and enjoy the park and take full advantage of the weather. We hope by then people can move around more safely in our community if we continue to work together to stay home to flatten this curve.”

-- Noelle Crombie; ncrombie@oregonian.com; 503-276-7184; @noellecrombie

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