Coronavirus: Boston biotech conference linked to 20,000 Covid-19 cases, study claims

Experts previously thought meeting was linked to around 90 infections

A biotech company conference held in Boston and attended by leaders from around the world may have led to 20,000 Covid-19 infections across the US, a new study has claimed.

Top managers at the Massachusetts-based drug company Biogen met at the Boston Marriott Long Wharf hotel in late February for a strategy a meeting, which has since become a known source of coronavirus spread.

Health experts initially estimated that the conference was responsible for around 90 infections. But a study published on the medrxiv.org portal on Tuesday ahead of peer review puts that figure closer at around 20,000.

Researchers from several research centres – including the Broad Institute of Harvard and MIT, Massachusetts General Hospital and the Massachusetts Department of Public Health – found that the virus at the heart of the outbreak was a strain of coronavirus with a specific genetic mutation, which is thought to have come from western Europe.

The conference was attended by around 175 of the company’s most senior employees from 26-27 February.

“Many factors made the conference an unfortunate perfect storm as a superspreading event,” Bronwyn MacInnis, a researcher at the Broad Institute who worked on the study, told CNN on Tuesday. “That the virus was introduced at the conference at all was unlucky.”

The researchers analysed viral genomes from 772 patients in Massachusetts, nearly all of whom tested positive for Covid-19 – the disease caused by the virus – within the first week of the outbreak.

They studied mutations in the genetic code of the virus and discovered 80 distinct genomes that were introduced into the state on a separate occasion from late January to early May.

Most of these, according to the study, came from other US states and western Europe, but did not lead to widespread illness. However, one of the genomes had a unique mutation that infected 289 – more than one-third – of the patients examined.

Researchers then traced this mutation back to the Biogen meeting, including 28 people known to have attended, worked at the hotel or were close contacts. In April, this sub-strain would hit at least two Boston homeless shelters, infecting 122 residents and staffers

It would go on to infect around 20,000 people, the researchers said.

“We’re not trying to point fingers [at Biogen],” MacInnis told The Boston Globe. “Some [viral] introductions fizzle out, others light fires. The circumstances of this event – the fact that it happened so early in the epidemic and the timing of where we were with Covid in the public consciousness – meant it had a disproportionate effect.’

MacInnis and her colleagues said the strategy meeting – an annual event for Biogen, which has an estimated 7,500 employees around the world and earns about $12 bn (£10.1 bn) in revenue – created the ideal effects for a super-spreader event.

“February 2020 was nearly a half year ago, and was a period when general knowledge about the coronavirus was limited,” Biogen said in a written statement to CNN on Tuesday.

“We were adhering closely to the prevailing official guidelines. We never would have knowingly put anyone at risk. 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.”