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Again and Again

A new analysis suggests there were multiple introductions of SARS-CoV-2 into the Boston area, WBUR reports.

Researchers from the Broad Institute collected samples from more than 300 COVID-19 patients at Massachusetts General Hospital between early March and early April for sequencing and analysis. In a working draft posted to, the researchers developed a phylogenetic tree of these samples, as compared to other SARS-CoV-2 samples. Based on this, they identified 30 different viral introductions into the area, including from Europe and other parts of the US, such as other parts of the Northeast, possibly New York City, and Washington State.

"The bans on travel did not stop introductions from the United States because it was already circulating in the community," Harvard University's William Hanage, who advised the research team, tells WBUR. "The phone call was coming from inside the building, to take a horror movie metaphor."

Similarly, a team from the University of California, San Francisco recently reported in Science there were multiple introductions of SARS-CoV-2 into Northern California.

Within their data, the Broad researchers also uncovered evidence of two superspreader events in the Boston area, one that occurred in late February — which WBUR traced to the Biogen leadership meeting — and one that occurred in early April at an assisted living facility.