What happens when a superspreader event in US keeps spreading

WASHINGTON • When the coronavirus stealthily infected 99 people after pharmaceutical firm Biogen held a two-day conference in February, it added the term "superspreader" to the pandemic lexicon.

Little did anyone know how super the spread would become.

A new analysis of the Biogen event at a Boston hotel has concluded that the coronavirus strains let loose 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 of biotechnology executives to Boston homeless shelters.

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 since October.

"When we hear these stories of clusters where 20 or 50 or 100 were affected, that does not account for what happens after," said genomic epidemiologist Bronwyn MacInnis at the Broad Institute of MIT and Harvard.

The analysis, by more than 50 healthcare experts and researchers based primarily in the Boston area, was published last Thursday in Science, the journal of the American Association for the Advancement of Science.

It is based on genetic analyses of the coronavirus taken from 28 people who attended the Biogen annual leadership conference.

At the time, only 30 Covid-19 infections had been confirmed in the United States. Biogen brought in 175 executives, including officials from Italy, Switzerland and Germany, for the meeting.

The analysis of the 28 cases determined that each person had been infected with a strain of the coronavirus, named C2416T, that had not previously been seen in the US.

The only known instances of the strain that preceded the Biogen conference involved two French patients, aged 87 and 88.

"We think there was a single importation into Boston, and that single importation was tightly linked to the spread that occurred at the conference," Dr Jacob E. Lemieux, an infectious disease specialist at Massachusetts General Hospital and a researcher at the Broad Institute, said.

By May, it was estimated that up to 56,000 known Covid-19 cases were directly tied to the Biogen conference. About 40 per cent were in Boston, but the C2416T strain was also carried across the country and elsewhere.

Fresh data included in the current analysis raised the estimate to as high as 300,000 cases in 29 states. The researchers estimated that the Cambridge strain of the virus was responsible for 1.9 per cent of all known cases in the US to October.

One of the study's more arresting findings was that within a month of the Biogen conference, the virus strains had made their way to Boston-area homeless shelters.

Tests at the shelters found 14 strains of the coronavirus, four of which appeared to have become superspreaders.

Dr Lemieux said this offers a lesson for those who take a casual attitude towards the coronavirus.

"We are so connected that we don't appreciate the linkages and interactions we have," he said.

In the months since the Biogen outbreak, the firm has come under fire for staging a global conference at a time when the likelihood of a pandemic was becoming clearer.

"The irony is that a large drug company was responsible for triggering the mother of all superspreader events that played a major role in making the virus endemic in the US, killing more than 3,000 Americans a day," said Mr John Carroll, editor of Endpoints News, which covers the biotech industry. "Top Biogen execs accidentally triggered a massive healthcare train wreck."

NYTIMES