Shortly after Covid-19 appeared in the U.S., one of the most well-publicized early “superspreader” events was connected to the international executive meeting of a large biotechnology company in Boston. Now, data from a genomic analysis of viruses taken from those infected at the meeting illustrate how such superspreader events can occur, even from a relatively small base.

The company, Biogen, based in nearby Cambridge, teamed up with academic institutions in April following a Covid-19 outbreak linked to the meeting, which took place in February at a Boston hotel. After initial reports that eight of those present at the meeting had become infected, the company told all 175 attendees to quarantine. Nevertheless, it was soon reported that multiple attendees at a biotech industry conference that had taken place shortly thereafter had also become infected, including prominent executives, having contracted the SARS-CoV-2 virus from infected Biogen executives.

The study, which looked at the conference as well as a superspreading event at a nursing home in Boston, was conducted by researchers at Harvard University, The Broad Institute of MIT and Harvard and other medical research institutions. It was posted on the preprint server, meaning it has not yet undergone peer review.

In an emailed statement, Biogen emphasized that it would never knowingly put people at risk and had been adhering to prevailing official guidelines in February 2020.

“When we announced our collaboration with the Broad Institute of MIT and Harvard in April, we explained that the Covid-19 pandemic had a very direct and personal impact on the Biogen community, and many colleagues were eager to help others through the pandemic by sharing de-identified biological and medical data to advance knowledge and the search for potential vaccines and treatments,” the statement read.

Ultimately, the study authors wrote, more than 90 cases of Covid-19 were diagnosed in people who had attended the meeting or had contact with them, and the researchers had a dataset from 28 of those cases. They found that all 28 displayed a genetic signature, C2416T, which originated in Europe and was then introduced into Boston through the conference, which included European Biogen executives.

“Taken together, this strongly suggests there was low-level community transmission of C2416T in Europe in February 2020 before the allele was introduced to Boston via a single introduction and amplified by superspreading at the conference,” the researchers wrote.

From there, it spread extensively in the Boston area, including in a local homeless shelter, also appearing in multiple other U.S. states and other countries in early March. Viruses originating from the Boston event soon showed up in Virginia, North Carolina, Michigan and Texas, as well as Sweden, Slovakia and Australia. Based on the rarity of other C2416T variants outside of Europe, the researchers assessed that most cases of that particular variant of the SARS-CoV-2 virus in the U.S. arose from the Biogen conference.

Photo: Orbon Alija, Getty Images

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