At the time, the slow mutation rate struck one young scientist as odd. “That really made my ears perk up,” said Alina Chan, a postdoctoral fellow at the Broad Institute in Cambridge, Massachusetts. Chan wondered whether the new virus was somehow “pre-adapted” to thrive in humans, before the outbreak even started. “By the time the SARS-CoV-2 virus was detected in Wuhan in late 2019, it looked like it had already picked up the mutations it needed to be very good at spreading among humans,” Chan said. “It was already good to go.” The hypothesis, widely disputed by other scientists, was the foundation for an explosive paper posted online in May 2020, in which Chan and her colleagues questioned the prevailing consensus that the lethal virus had naturally spilled over to humans from bats through an intermediary host animal. The question she helped put on the table has not gone away. In late May, President Joe Biden, dissatisfied by an equivocal report he had received on the subject, asked US intelligence services to dig deeper into the origins question. The new report is due any day now. In last year’s paper, Chan and her colleagues speculated that perhaps the virus had crossed over into humans and been circulating undetected for months while accumulating mutations. Perhaps, they said, the virus was already well adapted to humans while in bats or some other animal. Or maybe it adapted to humans while being studied in a lab, and had accidentally leaked out. Chan soon found herself in the middle of a maelstrom. An article in The Mail On Sunday, a British tabloid, ran with the headline: “Coronavirus did NOT come from animals in the Wuhan market.” Many senior virus experts criticised her work and dismissed it out of hand, saying she did not have the expertise to speak on the subject, that she was maligning their specialty and that her statements would alienate China, hampering any future investigations. Some called her a conspiracy theorist. Others dismissed her ideas because she is a postdoctoral fellow, a junior scientist. One virus expert, Benjamin Neuman, called her hypothesis “goofy.” A Chinese news outlet accused her of “filthy behaviour and a lack of basic academic ethics,” and readers piled on that she was a “race-traitor,” because of her Chinese ancestry. “There were days and weeks when I was extremely afraid, and many days I didn’t sleep,” Chan, 32, said recently at an outdoor cafe, not far from the Broad Institute. Chan’s story is a reflection of how deeply polarising questions about the origins of the virus have become. The vast majority of scientists think it originated in bats, and was transmitted to humans through an intermediate host animal, though none has been identified. Some of them believe that a lab accident, specifically at the Wuhan Institute of Virology in China, cannot be discounted and has not been adequately investigated. And a few think that the institute’s research, which involved harvesting bats and bat coronaviruses from the wild, may have played a role. It is an acrid debate. In May, 18 scientists, including Chan, published a letter calling for an investigation into the origins of the coronavirus. In July, a group of 21 virus experts — including one who had signed the May letter — posted a paper compiling the evidence for an animal source, saying there was “no evidence” of a laboratory origin. Scientists on all sides say they have been threatened with violence and have faced name-calling for their positions. The attacks were so fierce that Chan worried for her personal safety and started taking new precautions, wondering if she was being followed and varying her daily routines. The backlash made her fear that she had put her professional future in jeopardy, and she wrote a letter to her boss, in which she apologised and offered her resignation. “I thought I had committed career suicide, not just for me but for the whole group that wrote the paper,” Chan said. “I thought I had done a huge disservice to everybody, getting us mired in this controversy.” But Chan’s boss, Benjamin E Deverman, who was a co-author on the paper, refused to accept her resignation, saying only that they had been naive not to anticipate the heated reaction. Chan’s role has been so contentious that many scientists declined to discuss her at all. One of the few virus experts who was willing to comment flatly dismissed the possibility of a lab leak. “I believe there is no way the virus was genetically modified or person-made,” said Susan Weiss, co-director of the Penn Centre for Research on Coronaviruses and Other Emerging Pathogens at University of Pennsylvania, who also dismissed the possibility that the virus may have accidentally escaped the lab. “It is clearly zoonotic, from bats.” Others said Chan was brave to put alternative hypotheses on the table. “Alina Chan deserves the credit for challenging the conventional narrative and asking this question,” said Akiko Iwasaki, an immunologist at Yale University. “It is not easy for a junior scientist to openly challenge an established narrative.” (Iwasaki also credited a loose group of internet sleuths who go by the acronym DRASTIC.) “The degree to which the origin question became so inflammatory and polarised is mind-boggling,” Iwasaki said. “The fact is, we don’t know exactly where the virus came from, period. It was important to point that out.” As she sipped unsweetened ice tea and chatted about her ideas recently, Chan seemed an unlikely provocateur. She insisted that she was still on the fence about the virus’s origins, torn “50-50” between the natural route and lab accident hypotheses. No scientific journal ever published her paper. Determined to draw the attention to what she considered a critical question that had to be answered in order to prevent a future pandemic, Chan took to Twitter, mastering the art of tutorial threads and gathering followers. She is now in “worse shape” than before, Chan said: “Now I’m getting attacked from both sides. The scientists are still attacking me, and the lab leak proponents are attacking me, too, because I won’t go all the way and say it’s from a lab. I keep telling them I can’t, because there is no evidence.” Critics say Chan bears some responsibility for the backlash. Early last year on Twitter, she appeared to accuse scientists and editors “who are directly or indirectly covering up severe research integrity issues surrounding the key SARS-2-like viruses to stop and think,” adding, “If your actions obscure SARS2 origins, you’re playing a hand in the death of millions of people.” (She subsequently deleted the tweet.) Lab-leak proponents — who have called her “an apologist” for virus experts — have also been irked by the fact that Chan received so much credit for putting the question on the public agenda. Scientists at the Wuhan Institute of Virology said in early 2020 that they had found a virus in their database whose genome sequence was 96.2% similar to that of SARS-CoV-2, the new coronavirus. But it was internet sleuths and scientists who discovered that the virus matched one harvested in a cave linked to a pneumonia outbreak in 2012 that killed three miners — and that the Wuhan lab’s genomic database of bat coronaviruses was taken offline in late 2019.  Chan also landed a deal with Harper Collins, for an undisclosed amount, to co-author a book with Matt Ridley, a bestselling but controversial science writer who has been criticised for downplaying the seriousness of climate change. She denies accusations that she is writing the book for financial gain, saying she simply wants a complete record of the facts that will last longer than a Twitter feed. She plans to donate the proceeds to a COVID-related charity. “I don’t need money and frills,” she said. Chan was born in Vancouver, British Columbia, but her parents returned to their native Singapore when she was an infant. She was a teen when the SARS epidemic hit there. “People were dying of SARS, and it was nonstop on TV,” she recalled. “I was 15, and it really stuck with me. There were pictures of body bags in hospital hallways.” “When COVID started, many people in Boston thought it was no big deal, that flu is worse,” she said. “I remember thinking, ‘This is serious business.’ ” She returned to Canada after high school, studying biochemistry and molecular biology at University of British Columbia, and completing a Ph D in medical genetics. By age 25, she was a postdoctoral fellow at Harvard, and then she took a position working for Deverman, who is the director of the vector engineering research group at the Stanley Center for Psychiatric Research at the Broad Institute of MIT and Harvard. Chan is “insightful, incredibly determined and apparently fearless,” Deverman said, and she has an uncanny ability “to synthesise large amounts of complex information, distill all of the details down to the most critical points and then communicate them in easy to understand language.” A self-described workaholic, Chan married a fellow scientist during a break at an academic research conference a few years ago. “We took the morning off and went to city hall and came back to the conference, and my boss asked, ‘Where were you?’ ” she said. “I was like, ‘I got married.’ I don’t even have a ring. My mother is horrified.” She remains equivocal about the origins of the virus. “I’m leaning toward the lab leak theory now, but there are also days when I seriously consider that it could be from nature,” she said. “On those days, I feel mostly really, really sorry for the scientists who are implicated as possible sources for the virus,” she said. Referring to Shi Zhengli, the top Chinese virus expert who leads the research on emerging infectious diseases at the Wuhan Institute of Virology, Chan said, “I feel really sad for her situation. The stakes could not be higher.” © 2021 The New York Times Company