Lifestyle Health A Business Conference in Late February May Have Led to 20,000 Coronavirus Cases The 200 international attendees unknowingly spread COVID-19 after leaving the conference, held in Boston By Julie Mazziotta Julie Mazziotta Twitter Julie Mazziotta is the Sports Editor at PEOPLE, covering everything from the NFL to tennis to Simone Biles and Tom Brady. She was previously an Associate Editor for the Health vertical for six years, and prior to joining PEOPLE worked at Health Magazine. When not covering professional athletes, Julie spends her time as a (very) amateur athlete, training for marathons, long bike trips and hikes. People Editorial Guidelines Published on August 26, 2020 12:21 PM Share Tweet Pin Email Photo: Getty A business conference held in Boston in late February may have led to around 20,000 COVID-19 cases, after attendees unknowingly spread the virus. The event, a conference for biotech firm Biogen held between Feb. 26-27, included about 200 international attendees, including some from Italy, where the northern regions had just shut down to contain an outbreak of COVID-19. With just 15 reported cases in the U.S. at the time, the attendees shook hands, shared buffet food and kissed each other on the cheeks, The Washington Post reported, unaware that COVID-19 was already circulating amongst them. Once the conference ended, guests returned to homes in Massachusetts, North Carolina, Indiana and abroad, including Australia, Singapore and Slovakia. Just among the attendees and their close contacts, more than 90 people were diagnosed with COVID-19, “raising suspicion that a superspreading event had occurred there,” according to a new study. University of Alabama Reports More Than 500 Cases of Coronavirus Since Classes Began Last Week The high rate of transmission out of this single conference led 54 researchers from hospitals and institutions across Boston to sequence and analyze the strain of the virus found in the infected attendees, and compare that to the ones that circulated in the Boston area. They found that the conference strain of COVID-19 matched that of hundreds of people in the region, along with people as far as Alaska, Luxembourg and Senegal. The strain was also the same type found in about one-third of all COVID-19 cases sequenced in Massachusetts as of mid-July, indicating that the conference led to immense community spread. Just a month after the conference, more than 600 residents and staff at one of Boston’s largest homeless shelters were tested for COVID-19 as a safety precaution. Health officials were stunned to find that 230 people had already been infected, and genetic sequencing for this study determined that nearly two-thirds of the cases from the shelter were the same strain from the Biogen conference. “Our jaws dropped,” said Dr. Pardis Sabeti, a computational biologist at the Broad Institute and one of the lead researchers on the study told the Post. “It was the realization that these events really affect the most vulnerable among us.” The researchers say that the conference was a “perfect storm” of factors, from the international group to the close contact among attendees, to create a superspreader event. “That the virus was introduced at the conference at all was unlucky," Dr. Bronwyn MacInnis, a researcher at the Broad Institute who worked on the study, told CNN. "When it happened was critical: it was scheduled just as we were collectively beginning to appreciate the imminent threat of COVID at home — if it had been a week later the event likely would have been cancelled.” MacInnis noted that the conference occurred before COVID-19 testing was available in the U.S., before social distancing was understood and well before the Centers for Disease Control recommended masks. At Least 103 New Coronavirus Cases in 8 States Linked to South Dakota Motorcycle Rally Based on the spread of the virus among attendees and the lack of COVID-19 restrictions at the time, the researchers estimate that this conference led to 20,000 infections. “This is not a rigorous estimate but does communicate the scale,” MacInnis said. “If tens of thousands of individuals seems large, it is important to point out that it is in context of a pandemic that has infected tens of millions of people.” The conference and the cases that followed should serve as a lesson on how swiftly COVID-19 can spread, the researchers said. “We didn’t know better,” said Jacob Lemieux, a physician and infectious-disease expert at Massachusetts General Hospital and lead author of the study told the Post. “The difference now is there is increasing scientific evidence to show what can happen from a single event like that. We do know better. So we need to learn the lesson.” As information about the coronavirus pandemic rapidly changes, PEOPLE is committed to providing the most recent data in our coverage. Some of the information in this story may have changed after publication. For the latest on COVID-19, readers are encouraged to use online resources from CDC, WHO, and local public health departments. PEOPLE has partnered with GoFundMe to raise money for the COVID-19 Relief Fund, a GoFundMe.org fundraiser to support everything from frontline responders to families in need, as well as organizations helping communities. For more information or to donate, click here.