Peter Bergethon, director of digital and quantitative medicine at Biogen, returned home with his wife, a doctor specializing in infectious diseases.
A vice president of Biogen in the Alzheimer franchise and her husband attended a party the following Saturday night at a friend’s house in Princeton, New Jersey, with about 45 other people.
They celebrated a feast in the Greek Orthodox calendar, the end of the carnival season, with special sweets and traditional dances that involved holding hands in a circle. Although the celebrations in Greece have been canceled, the party in New Jersey continued as White House officials had just declared that the virus in the United States was under control.
That night, Allana Taranto, a photographer who covered the executive meeting for Biogen, celebrated her 42nd birthday with her boyfriend and another couple.
By the weekend, however, some people at the company had already started to feel sick.
Jie Li, a 37-year-old biostatistician who worked on the Alzheimer’s medication team, experienced chills, coughing and muscle aches. She was too young to attend the company executive conference, but her boss went and reported to the office afterward.
On March 2, the following Monday, the company’s chief medical officer sent an e-mail informing everyone at the executive meeting that some people had become ill and telling them to contact a health care professional if they felt sick.
“We acted quickly,” said Mr. Caouette.
However, on the same day, the company’s top four leaders attended a huge healthcare conference hosted by the investment firm Cowen. At another Boston Marriott, they held meetings in hotel rooms with potential investors. Another participant who met with some of the same investors said he heard that the Biogen team members looked sick.