A single biotech meeting back in early February is responsible for nearly 20,000 cases of COVID-19 in Massachusetts, according to a new study.  

As the Boston Globe reports, an international meeting of Biogen leaders at Boston's Marriott Long Wharf hotel became a “super-spreading event,” resulting in far more than the original 99 cases previously reported from the event. 

In response to the study, Biogen acknowledged that at the time of the event six months ago, the company’s understanding of COVID-19 was limited. It didn’t dispute the findings of 20,000 conference-related cases.

“We never would have knowingly put anyone at risk,” Biogen said in a statement, per the Globe. “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.”

From the study, researchers came to their 20,000 estimate based on viruses isolated from 772 local patients—mostly from Essex, Middlesex, Norfolk, and Suffolk counties. The large estimation is not included in the study, which has yet to be peer-reviewed for publication. Using the unique genetic signature of the confirmed conference-related cases, scientists found more than a third of COVID-19 cases in the study came from the hotel meetings in February. 

“I’m confident that the scale for measuring this event is in the tens of thousands,” Dr. Jacob Lemieux told the Globe. Lemieux is an infectious disease physician at Massachusetts General Hospital and one of the many scientists who helped write the study. 

The study chose not to mention Biogen by name. Instead of focusing criticism against one company, this research serves as a warning for others looking to hold big gatherings as COVID-19 continues to spread across the country.