Update: The Boston Marriott Long Wharf, the hotel that hosted a Biogen company gathering linked to a majority of the coronavirus cases in Massachusetts, is closing temporarily. In a letter to guests on Thursday, the hotel said it made the decision with the Boston Public Health Commission.

Among the coronavirus numbers that Massachusetts officials have shared recently, one is particularly striking: Of the state's 95 cases detected as of late Wednesday, they say 77 stemmed from a meeting that the Cambridge biotech company Biogen held in late February.

In public health parlance, the Biogen meeting is looking like a "superspreading event."

Perhaps you've heard of Typhoid Mary, the New York cook who spread Typhoid fever in the early 20th century. She used to be seen as an anomaly, because it was thought that everyone was more-or-less equally prone to spread a disease.

But now, it’s known that “superspreaders” or “superspreading events” are common in epidemics, including SARS in 2003 and a measles outbreak in Canada in 2011 that appeared to stem from one patient's stint in the Montreal airport.

Yale professor Nicholas Christakis, a physician and sociologist who studies networks, says the current outbreak in Italy also stemmed from a "superspreader."

"We know from genetic analyses in Italy that the epidemic there was started, we think, by two people, one of whom gave it to 43 other people," he says.

"The question arises," he says, "when we see a superspreading episode like this episode at Biogen appears to be, what's the cause of it? Is it just chance? Or is it something to do with the particular circumstances?"

Though superspreading has been documented in one epidemic after another, it’s not well understood.

"We certainly think biology plays a role," says Dr. Ashish Jha, a professor of health policy at the Harvard Chan School of Public Health. "Some people end up having a very high viral load and then they shed a lot more virus than other people. It may be something with your immune system, something to do with how that immune system is reacting to the virus."

Initial findings suggest the coronavirus could be quite contagious early on, possibly even before symptoms show up or get bad.