BOSTON — Gov. Charlie Baker on Tuesday declined to characterize the commonwealth as being at the start of a "second wave" of COVID-19 transmission.

 

But he had no trouble identifying the source of a recent surge in the spread of the novel coronavirus.

 

"I think it's really important to point out once again … and Dr. [Deborah] Birx said the same thing when she was here last week: The biggest single issue that's driving case growth is familiar people being familiar with each other," Baker said Tuesday afternoon. "She talked, in particular, when she talked to us, about something we've seen in our own data, which is a really significant increase in positive cases among people in their 20s and 30s."

 

Birx, who visited several college campuses in New England, is the White House's response coordinator for its Coronavirus Task Force.

 

On a day when Baker, Lt. Gov. Karyn Polito and their secretaries of education, health and economic development spent most of their time recapping the commonwealth's progress since March, the governor also acknowledged that Massachusetts is starting to see an overall increase in positive tests for COVID-19.

 

"I think one of the things that's critically important for this is to recognize and understand especially with respect to young people, that that community, more than any other at this point, is driving the largest single increase in cases," Baker said. "The good news is: The vast majority of them don't get as sick as someone over the age of 60 would.

 

"But many do, and they do have the potential to pass it on to other people in their family or their network who are older and, for whom, getting the virus could be a very terrible thing. I think that, in many ways, is one of the more important differences between where we are now and where we were in the spring."

 

Baker brought up the pattern of transmission among Millennials (those born between 1981 and 1996) in answer to a question about whether his administration would consider rolling back some of the state's reopening plan, as an emergency department physician at Boston's Brigham and Women's Hospital recommended last week.

 

The governor said that the increase in cases in recent weeks is not attributable to "formal activities" like indoor dining and shopping but to "informal gatherings," especially among younger Bay Staters. He cited evidence from the commonwealth's contact tracing initiative that demonstrates where the real source of transmission lies.

 

"There's no evidence that [indoor dining at restaurants] is what's driving our cases," Baker said in response to a reporter's question. "I'm not going to stop doing things just because somebody doesn't like them. Somebody needs to actually demonstrate in data that something is actually driving cases.

 

"Right now, the thing that's driving cases is young people -- not necessarily college kids, we're talking kids that are out of college -- who are spending a lot of time with each other in close quarters, apartments, rooftops, places like that. They're not social distancing. And they're passing the virus around."

 

Going forward, there are dangers that lie ahead for Bay Staters of all ages as those informal -- and often cross-generational -- gatherings move out of the back yards and into the living rooms as the holidays approach.

 

"We are probably going to have to talk about Thanksgiving at some point," Baker said. "I don't have what it is we should be saying about it today. But that's certainly going to be a conversation that I think a lot of people should take seriously.

 

"Thanksgiving is going to be the source of some interesting conversations, not only because of the family gatherings but also because it's one of the biggest travel days, historically, of the year, and that presents all kinds of other issues."

 

As he does routinely, Baker praised Massachusetts residents for the economic sacrifices they've made and the lifestyle changes they've adapted to help limit the spread of the virus. But he continued to hammer home a message about the need for continued vigilance, particularly as the weather turns and outdoor activities become less of an option.

 

"If you have a neighbor who's been traveling out of state, you're probably better off not watching the Patriots game with them on Sunday, unless they've been tested and they've tested negative," he said.

 

"People get that they're supposed to wear a mask when they go out, and, by they way, that's different from what it was in March and April. … They get the fact that they're supposed to social distance. They get the fact that if they can't social distance they need to [wear a mask]. They get the fact that they need to wear a mask if they go into a store. They get all that, and it's working.

 

"The challenge is all that other time we spend, in some cases with people who may have been out and about with others where they weren't social distancing and they weren't wearing a mask. And especially when you get into the younger communities, the 20- and 30-somethings, they do pick this thing up. They often are symptomatic. But they do carry it, and they will transmit it."