When Large Gatherings Go Bad In the Time of COVID

When large gatherings go bad in the time of COVID, they go really bad.

Researchers have determined that a conference held by the firm Biogen in Boston in February may have ultimately led to 300,000 COVID-19 infections. 

A new analysis of the Biogen event at a Boston hotel has concluded that the coronavirus strains loosed at the meeting have since migrated worldwide, infecting about 245,000 Americans — and potentially as many as 300,000 — by the end of October.

The virus strains spread to at least 29 states. They were found in Australia, Sweden and Slovakia. They wended their way from a room packed with biotechnology executives to Boston homeless shelters, where they also spread widely among occupants.

Those are just the infections. How many people were killed by the virus strains cannot be reliably estimated. Nor do the figures include infections among the six million Americans who have tested positive for the coronavirus since October, as infections have spiked.

“It’s a cautionary tale,” said Bronwyn MacInnis, a genomic epidemiologist at the Broad Institute of Harvard and M.I.T. “When we hear these stories of clusters where 20 or 50 or 100 were affected, that does not account for what happens after.”

This dramatically shows the importance of curtailing large gatherings until the pandemic is under control; in other words, until a large enough portion of the population is vaccinated that superspreader events are unlikely to occur. 

One of the study’s more arresting findings was that within a month of the Biogen conference, the virus strain introduced there had made its way to Boston-area homeless shelters. Tests at the shelters, affiliated with the Boston Health Care for the Homeless Program, found 14 strains of the coronavirus, four of which appeared to have become superspreaders. The researchers found that two clusters of cases that resembled superspreader events were associated with the virus from the conference.

Dr. Lemieux said that offered a lesson for those who take a casual attitude toward the coronavirus. “That’s just the interconnectivity of society,” he said. “Our intuition about how disconnected we can be is not reliable. We are so connected that we don’t appreciate the linkages and interactions we have.”