By Joseph Walker

An international meeting of Biogen Inc. managers last February likely helped spread the novel coronavirus from Boston to thousands of people as far away as Michigan, Virginia and Australia, according to researchers who conducted a new genetic analysis.

By identifying the genetic profile of the virus that infected meeting attendees or their contacts, the researchers found that the Biogen conference was a "superspreader event," in which clusters of infections are created through rapid transmission.

From Boston, the virus strain spread out around Massachusetts and eventually to cities around the U.S. and the world, the researchers said in a paper posted online Tuesday in an database for early versions of scientific papers.

Among the nearly 12,000 virus samples from around the U.S. that the researchers analyzed, the Biogen strain represented 2.7% of cases, they said. The strain represented 1.7% of more than 56,000 global samples.

"Any infection that happens early on in an outbreak like this, where it's exponential, it's either going to peter out very quickly or wind up infecting a lot of people very quickly," said Stephen Schaffner, a study co-author and computational biologist at the Broad Institute of Harvard and MIT.

The paper hasn't yet been published in a peer-reviewed journal.

"February 2020 was nearly a half year ago and was a period when general knowledge about the coronavirus was limited," a Biogen spokesman said. "When we learned a number of our colleagues were ill, we did not know the cause was Covid-19, but we immediately notified public-health authorities and took steps to limit the spread."

The coronavirus strain identified by the researchers likely originated in Europe before being introduced to the Boston area, their study said.

The strain was then spread at the two-day strategy meeting of 175 Biogen senior managers, according to the study, some of whom had traveled from other parts of the U.S. and from around the world.

The meeting took place at the Boston Marriott Long Wharf hotel. One unnamed company executive tested positive after the meeting and went into isolation, The Wall Street Journal has reported. Other managers traveled to gatherings of investors and doctors.

To conduct the study, scientists analyzed virus samples from 772 patients collected by the Massachusetts Department of Public Health and Massachusetts General Hospital between late January and May, including 28 cases linked to the Biogen meeting.

The genetic profile of the virus samples taken from patients linked to the Biogen conference eventually became one of the most common found in Massachusetts, accounting for more than a third of samples the researchers analyzed, they said.

The strain was then exported to states including North Carolina and Texas, as well to Sweden and Slovakia. The researchers also found evidence that the strain led to community transmission -- where new infections can't be traced back to other infected or high-risk individuals -- in Michigan, Virginia and Australia.

Write to Joseph Walker at joseph.walker@wsj.com