NEW STUDY: Genetic data show how a single superspreading event sent coronavirus across the nation and world

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Tue, 2020-08-25 11:28 — mike kraft

Genetic data show how a single superspreading event sent coronavirus across Massachusetts — and the nation Sarah Kaplan, Chris Mooney Washington Post

None of the biotech executives at the meeting noticed the uninvited guest. They had flown to Boston from across the globe for the annual leadership meeting of the drug company Biogen, and they were busy catching up with colleagues and hobnobbing with upper management. For two days they shook hands, kissed cheeks, passed each other the salad tongs at the hotel buffet, never realizing that one among their number carried the coronavirus in their lungs.

By the meeting’s end on Feb. 27, the infection had infiltrated many more people: a research director, a photographer, the general manager for the company’s east division. They took the virus home with them to the Boston suburbs, Indiana and North Carolina, to Slovakia, Australia and Singapore.

Over the following two weeks, the virus that circulated among conference attendees was implicated in at least 35 new cases. In April, the same distinctive viral sub-strain swirled through two Boston homeless shelters, where it infected 122 residents.

Scientists know all this thanks to a mistake made during the coronavirus’s replication process — a simple switch of two letters in the virus’s 30,000-character genetic code. This mutation appeared in two elderly patients in France at almost exactly the same time that genetically matching viruses were sickening dozens of people at the Biogen meeting. After the conference, each time the infection spread, the mutation spread with it.

Now, a sweeping study of nearly 800 coronavirus genomes, conducted by no less than 54 researchers at the Broad Institute, Massachusetts General Hospital, the Massachusetts Department of Public Health and several other institutions in the state, has found that viruses carrying the conference’s characteristic mutation infected hundreds of people in the Boston area, as well as victims from Alaska to Senegal to Luxembourg. As of mid-July, the variant had been found in about one-third of the cases sequenced in Massachusetts and 3 percent of all genomes studied thus far in the United States.

The study, which was added Tuesday to the preprint website MedRxiv, is probably the largest genomic analysis of any U.S. outbreak so far and is among the most detailed looks at how coronavirus cases exploded in the pandemic’s first wave. ...

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