Updated at 2:30 p.m.

Gov. Charlie Baker says he's keeping a close eye on record-setting numbers of positive cases of COVID-19 in Massachusetts, but that he's not convinced the second surge of the virus is severe enough to roll back the state's reopening plan.

Baker said Wednesday's new record number of positive tests — 4,613 in one day — is concerning, but that it also reflects the record-setting volume of testing the state has been conducting. There were 105,845 tests conducted Wednesday, with a 4.36 percent positive rate.

"We're going to continue to pay attention to the data that's released every day, but the one thing I would say is one day does not make a trend," Baker said at a press briefing at the Worcester DCU Center field hospital, which has reopened to assist UMass Memorial Medical Center as its ICU fills up with COVID patients. "The ratio of people in the ICU to the total number of people hospitalized is down significantly from what we saw back in the spring. Still, obviously, as cases rise, we can expect our hospitals to continue to face additional strain on the system."

ABC News reported Wednesday that the White House Coronavirus Task Force warned governors that anyone who celebrated Thanksgiving outside their immediate household should be assumed to be infectious and dangerous to others.

When asked directly if he's considering rolling back the state's reopening from the current second stage of phase three to the first stage or to an even earlier phase, Baker reiterated his COVID-era mantra — he's going to "follow the data."

"We're not going to make decisions that aren't going to give people lead time with respect to how they respond," Baker added.

Baker said many communities are already a step behind healthier sections of the commonwealth because they don't meet the qualifications to take part in step two of phase three.

"This is going to be a constant balancing act for us here in Massachusetts, and we get that," Baker said.

Even though UMass Memorial's beds are filling fast, the facility has not yet seen the results of transmissions that may have occurred over last week's Thanksgiving holiday, said Eric Dickson, president of UMass Memorial Health Care. Dickson expects the positivity rate to rise even higher Thursday and Friday, with hospitalizations lagging behind three to four weeks after the holiday.

"We have definitely not seen, from our perspective, the worst of what we're going to see for hospitalizations," Dickson said.

While in Worcester, Baker announced that a field hospital in Lowell staffed by Lowell General Hospital will open in the coming weeks.