MONROE — Nearly 60 people imprisoned at the Monroe Correctional Complex were in medical isolation this week due to a COVID-19 outbreak in a medium-security unit of the state prison.

The entirety of the Twin Rivers Unit is now under quarantine. Visitation is halted until the quarantine ends, corrections officials said.

One incarcerated person and one employee tested positive for the virus Monday.

Subsequently, all those housed in Unit A of the facility were tested for COVID-19 and results for 33 people came back positive, according to a memo issued Wednesday.

On Thanksgiving, additional confirmed cases were found among the incarcerated population in the facility’s other three living units, according to a Department of Corrections spokeswoman.

As of Friday morning, 57 people had tested positive for COVID-19 and been moved into the prison’s medical isolation unit. Two corrections staff from Unit A tested positive. No one had been hospitalized in the current outbreak, DOC spokeswoman Jacque Coe said in an email.

Twin Rivers is one of five facilities in the Monroe prison complex and was the only one affected as of Friday. It has roughly 800 beds split evenly among four housing areas. Units A and B, where the outbreak began, are for medium security. Units C and D are for minimum custody. Twin Rivers housed 752 prisoners on Friday.

The source of the outbreak was not known. Pinpointing the exact manner of transmission is very difficult due to the number of staff and incarcerated people in Twin Rivers, Coe said.

Those who tested positive this week were placed in the prison’s medical isolation unit. The length of isolation varies under department guidelines. People are able to move out of the unit 14 days after the absence of any COVID-19 symptoms, Coe said.

Under current department guidance, asymptomatic vaccinated patients could exit as early as 10 days from the date of their test. Unvaccinated or partially vaccinated patients must stay in at least 14 days or 20 days, respectively, from their COVID test, as long as their symptoms are improving.

“These steps are meant to minimize the impacts that our response will have on our incarcerated population,” incident commander Lisa Anderson wrote in a memo to inmates Wednesday. “As we move forward, you can expect to see a cohort (limited group) standard for day rooms, outside recreation, dining, and shower/bathroom areas. Serial testing will continue for the incarcerated population.

“It is our hope in taking these measures,” she wrote, “that we can cut down on the number of potential exposures and reduce the amount of time it will take to get back to a new normal with our operations.”

Monroe has tallied its share of coronavirus infections. As of Wednesday, there had been 570 confirmed COVID cases among inmates and 232 among staff since the start of the pandemic in 2020, according to corrections department data. The last big outbreak occurred in the final week of 2020, when 126 prisoners and eight staff contracted the virus.

That’s right around the time Moderna vaccines began to be administered in Washington prisons.

At the Monroe Correctional Complex, 97.3% of employees, including corrections officers, had been vaccinated or had an exemption plus accommodation to keep working as of Nov. 15. Excluding those with exemptions, the rate was 99.1%, according to data compiled by the Office of Financial Management.

As of Tuesday, the Department had administered either the Moderna or Johnson & Johnson vaccine to 9,825 prisoners in state correctional facilities since vaccines became available nearly a year ago. Of the total, 88 doses of Johnson & Johnson and 4,221 doses of Moderna had been given to prisoners at Monroe.

Washington’s total prison population was 12,809 in September.

Jerry Cornfield: jcornfield@heraldnet.com; 360-352-8623; Twitter: @dospueblos.