BOISE, Idaho (AP) — Hospitals are preparing for a potential influx of older patients after a recent spike in coronavirus infections among young people visiting bars who are likely bringing the illness home to their parents and grandparents, a health expert said Friday.

Barton Hill, vice president and chief quality officer of St. Luke’s Health System, said most of the people testing positive recently have been in their 20s and 30s.

Most aren't “sick enough to need hospitalization,” he said, but noted several people in their 20s did need to be hospitalized. “I think probably it's going to be the family units where it's going to spread to more at-risk populations.”

Young adults working in senior living facilities also have the potential to bring the illness into that vulnerable population, Hill said.

For most people, the coronavirus causes mild or moderate symptoms, such as fever and cough that clear up in two to three weeks. But for some — especially older adults and people with existing health problems — it can cause more severe illness, including pneumonia, and death.

"The older patients are going to be the ones who are really going to put the pinch on our health care," Hill said.

Idaho’s daily confirmed coronavirus cases jumped by about 10% to nearly 5,000 on Friday, according to a tally by Johns Hopkins University that included 90 deaths. And the percentage of people testing positive jumped from 2.8% to 7.8% over the last two weeks, according to the COVID Tracking Project.

Idaho had been progressing through Republican Gov. Brad Little's four stages of reopening during the pandemic. But Little on Thursday said the recent surge in infections meant he was keeping the state at stage 4. It had been set to expire Saturday.

Little said he was primarily concerned about making sure there are enough ventilators and beds in intensive care units to handle extremely ill coronavirus patients. Both those numbers look good at the moment.

Little also said the state was switching to a regional response allowing local officials to decide on restrictions with his oversight. Ada County, where many of the young people became infected at bars, on Wednesday moved back to stage 3 and shut down the bars.

Bars were allowed to open May 30 after being closed since late March, and people had pent up energy.

“The weekend of June 5, 6 and 7, that bar scene in Boise was like spring break,” Hill said.

He said each infected person infects about three more. That could slow in Ada County now that more restrictions have been put in place. But nearby Canyon County has bars open.

“I think it's only a matter of time before Canyon County looks like Ada County,” Hill said.

He said hospitals had returned to doing elective surgeries, which can use up medical supplies as well as lower the number of ventilators and intensive care unit beds available. But elective surgeries could be stopped if older coronavirus patients start filling hospitals, Hill said.

“We're working to make sure that we have adequate supplies,” he said. “You do that all the time, but now there is an increased urgency.”

State prison officials are also bracing for additional cases. There are at least three confirmed COVID-19 cases among Idaho’s prison inmates, all of them among offenders living in the same area of the Idaho State Correctional Center, Idaho Department of Correction Director Josh Tewalt wrote in a prepared statement Thursday. At least 13 IDOC staffers have also tested positive for the illness, and 27 more are out of work because they have had close contact with another staffer who tested positive.

Prison officials are starting their first mass testing event for inmates at the Idaho State Correctional Center next week, Tewalt said.

“If we’ve learned anything from the states that have been dealing with COVID-19 in their facilities for months now, it’s that where there is one positive case inside a prison, there are likely others,” Tewalt wrote. “We’re learning that first-hand now, and I expect cases will be on the incline for some time to come.”