SALEM, Ore. (AP) — Oregon reported 24 more deaths from COVID-19 on Tuesday, a record high for a single day in the state.

The Oregon Health Authority said the “grim milestone” underscores that people should wear masks, keep physical distance and keep gatherings small. The increase raises the state’s known death toll to 936.

Officials in Silverton, a town east of Salem, are trying to monitor a potential outbreak among firefighters. The situation has underscored a weakness in Oregon's response to the pandemic: a lack of a system for getting first responders tested rapidly, said Assistant Chief Ed Grambusch of the Silverton Fire District.

A member of the fire district who was taking part in training on Nov. 21 has been diagnosed with COVID-19. Twenty people who were trainees or instructors may have had a high risk exposure.

All have been advised to self-quarantine and get tested. When Grambusch, who coordinates local responses to infectious disease outbreaks, called the Oregon Health Authority, the agency confirmed he needed to talk to Marion County health officials about rapid testing. The county officials told him they don't know of any such system, Grambusch said.

“The problem is — this is a big frustration of mine — is that we don’t have a system for rapid testing of our first responders,” Grambusch said. “And I’m just not sure why that’s the case. I would hope that we could send an email or make a phone call — one phone call — and send someone in to get a rapid test."

Firefighters and paramedics instead need to make appointments at pharmacies or with their health-care providers, which can take days, he said.

State health officials did not immediately respond to questions about the situation.

The health authority announced Tuesday that a technical issue has created a backlog of unprocessed test results.

It also reported 1,233 new confirmed and presumptive cases of COVID-19, bringing the known total in Oregon to 76,654. There may be many more cases that authorities don't know about.

Effective Thursday through Dec. 17, 25 counties will be in the extreme risk level, the most severe of four levels, Gov. Kate Brown announced. Two weeks ago, 21 counties were designated extreme risk.

“Counties that are facing extreme risk of virus spread will need to continue with strict health and safety measures,” Brown said.

Those whose deaths were announced Tuesday had died as far back as Oct. 28 but most deaths occurred in the final two weeks of November. Some died within a day or two of testing positive and one died the same day. They ranged in age from 56 to 96.

Oregon Health and Science University, meanwhile, is seeking Portland-area residents to participate in a research study evaluating a potential COVID-19 vaccine developed by Oxford University and the pharmaceutical company AstraZeneca.

The clinical trial seeks to enroll 30,000 participants to evaluate the safety and effectiveness of the investigational vaccine known as AZD1222. The experimental vaccine is designed to be given in two injections that are administered about four weeks apart.

The study strives to enroll a diverse group, prioritizing those who are older than 55 and people of color, the Portland university said. Two-thirds of participants will receive the experimental vaccine and one third will receive a placebo.

AstraZeneca and Oxford University on Nov. 25 acknowledged a manufacturing error raised questions about preliminary results of their experimental vaccine. Oxford University said some of the vials used in the trial didn’t have the right concentration of vaccine so some volunteers got a half dose.

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