BOSTON (CBS) — Coronavirus cases in Massachusetts have “ticked up,” Gov. Charlie Baker said Monday. He said people taking advantage of the warm weather should not let their guard down during the coronavirus pandemic.

“Positive test rates have ticked up, going from about 1.7 to about 2 percent,” Baker said. “Obviously we prefer to see zero new cases of COVID, but we know that’s just not going to be the case until we have a medical breakthrough, like a vaccine.”

Massachusetts now has more than 108,000 confirmed coronavirus cases after reporting 273 more positive tests and 19 additional deaths Sunday.

Baker linked the uptick to the continued reopening of businesses in Massachusetts and people enjoying the warm weather.

“There’s simply a lot more mobility out there and some of that is a result of the economic activity that’s associated with opening up some of our Commonwealth businesses and employers,” he said. “But some of it’s also just people being out and about; it’s warm out. And people, generally speaking, are probably in more contact with people now than they were in the month of April, May, and even June.”

Baker said health officials are aware of some “small clusters” of coronavirus in the state associated with gatherings.

“If we let our guard down, COVID will take advantage of that,” he said.

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Baker stressed that Massachusetts residents “should be enormously proud” of the steps they’ve taken to lower the positive rate over the last several months.

“Since we started reopening, we’ve gone from about nine or 10 percent positive test rate, at the point we reopened, to the point now where it’s below 2 percent,” he said. “But the last thing we can do is starting to think that means there isn’t COVID in Massachusetts, around and among us.”

Massachusetts is expanding its free testing initiative in communities that have been reporting higher positive rates while conducting fewer tests. The cities and towns offering free tests are Agawam, Brockton, Chelsea, Everett, Fall River, Lawrence, Lowell, Lynn, Marlborough, Methuen, New Bedford, Randolph, Revere, Springfield, Taunton, and Worcester.

Residents can visit to find a testing site near them and learn how to make an appointment.

Baker said in response to a reporter’s question that Massachusetts will not be reversing its reopening steps at this time in response to the recent uptick.

“I think at this point in time the most important thing we need to do is continue to do the things that got us here in the first place,” he said. “The data we’ve seen about where the clusters have come from has had a lot more to do with people just sort of letting down their guard.”

Starting Saturday, a new travel order will take effect in Massachusetts that requires visitors to quarantine for 14 days unless they are coming from an exempt, lower-risk state or can provide a negative COVID-19 test from the last 72 hours. Violators face a potential fine of up to $500 per day.