A Biogen management meeting held in Boston in late February has spawned 108 confirmed or presumptive positive cases of the novel coronavirus—and has now led to a criminal investigation.

Monday, Beijing police said they had filed an investigation of a woman surnamed Li for hiding her health status when entering China, a potentially criminal offense. A Biogen spokesperson has confirmed to FiercePharma that it believes “Ms. Li is a U.S.-based Biogen employee who made a personal decision to travel to China.”

The Beijing government first disclosed Li’s case during a recent coronavirus press briefing. While keeping the identity of her employer under wraps at the time, authorities said she attended a company meeting Feb. 26-27, the exact days Biogen’s 175-person leadership conference took place.

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Li, 37, a Chinese citizen and permanent Massachusetts resident, had been denied a COVID-19 test in that state, Chinese authorities said. According to local officials, she flew back to Beijing with known symptoms of COVID-19.

According to a representative from Air China, Li took the airline’s CA988 flight from Los Angeles to Beijing on March 12. About an hour after takeoff, Li told the flight attendant she wasn’t feeling well. Though she admitted a brief history of fever the week prior, her temperature at the time proved normal. Still, the attendant moved her to a quarantine zone at the tail of the aircraft.

Li also told the steward she was traveling alone and hadn't taken any medicine before the flight. The thing is, those statements weren’t true. Two hours before landing, Li again approached the flight attendant. This time, she acknowledged her husband and son were onboard—several rows ahead—and that she had taken antipyretic before boarding the plane. And she admitted a colleague at her U.S. firm had been infected.

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On March 13, Li was confirmed infected with SARS-CoV-2, and her two family members were put in the suspected category, according to Beijing’s CDC. Because of her belated disclosure, 59 people on the flight have been identified as close contacts at risk of infection.

Why did Li travel to China when she had already fallen ill with symptoms consistent with the coronavirus? Basically, she says she was denied a coronavirus test.

According to Chinese authorities, Li said she started showing symptoms such as chills on March 1 and went to see a doctor in Massachusetts two days later. She was given Roche’s Tamiflu, an influenza medication.

Two chest scans on March 5 and March 10 showed no abnormalities, but the one on March 11 returned with signs of lung infection. She requested to be tested for SARS-CoV-2 three times, but was rejected.

By March 6, there were already confirmed cases linked to the Biogen meeting. Having symptoms and exposure to an infected person clearly met the two main criteria for coronavirus testing. Chinese health officials didn’t explain why Li was denied one in the U.S.

Right now, Li’s being treated at a designated hospital in Beijing, while her husband and son remain on observation. Beijing police said it has put Li’s case on file for suspected obstruction of prevention of infectious disease.

In a statement to FiercePharma on Monday, Biogen said, “We are deeply dismayed by the situation as reported by the media in China.”

In the COVID-19 update on its website, the Big Biotech says it has taken several actions, including “[q]uarantine of anyone who attended the February meeting in Boston.” That company instruction came in early March, before Li made her trip back to China.

Editor's Note: The story has been updated with a statement from Biogen.