BOSTON (CBS) – Massachusetts Gov. Charlie Baker said his biggest concern about the spread of coronavirus in the state comes from “unmanaged” events like social gatherings.

Baker was asked about a new report that indicates about that about 20,000 coronavirus cases may have been linked to the Biogen employee conference in February at the Marriott Long Wharf in Boston.

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“Well we said for a while now that our biggest concern at this point is unmasked, undistanced, unmanaged events,” said Baker, noting how much new information has developed about masks and social distancing since the conference.

Baker said contact tracing has shown that in areas where cases rise, it is usually not coming from places like stores, but rather what is described as an “organized activity” where people don’t wear masks or practice social distancing.

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“The big challenge for us is to is to bring that kind of discipline to other kinds of events where people clearly haven’t been distancing haven’t been wearing masks and a lot of these involve what I would describe as events in which people are familiar with one another and they behave like they’re familiar with one another,” Baker said. “As difficult as it is for all of us, the hugging, the high fiving, the singing along to the songs, whatever it might be, indoors or outdoors, particularly in close quarter environments is just the wrong thing to be doing when you’re trying to work your way through a pandemic.”

Baker pointed to a cluster of recent cases stemming from a wedding in Maine as a recent example. He also said there was a wedding in Rhode Island attended by Massachusetts residents, and everyone who went to that wedding except one person tested positive for COVID-19.

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“There are reasons why we focus so hard on face coverings and distancing and hand washing and wiping surfaces. Because these are the things that we all have the power and the control over to limit the spread of the virus and we should continue to do them,” said Baker.