text: On January 3, the last day of her Christmas vacation, Dr. Vanessa Allen absconded to a nearby café. The chief of microbiology and laboratory science at Public Health Ontario (PHO) wanted to catch up on work before Monday, and she needed somewhere quiet, secluded, and, most importantly, away from her twin three-year-olds to do it. ("I love them," she said, laughing. "But they're little monsters.") She was checking her emails when she saw an alert about the worsening situation in Wuhan. Allen had worked in a hospital during the SARS outbreak, had seen the devastation and disorganization first-hand, and had joined PHO because of the agency's mandate to anticipate and better respond to outbreaks. Launched in 2008, PHO is a direct result, as the organization's first annual report puts it, of "Ontario's wake-up call from a series of outbreaks." Those included SARS, of course, but also Legionnaires' disease and the E. coli outbreak in Walkerton. When Allen joined the organization that same year, the province was in the midst of a listeriosis outbreak linked to contaminated cold cuts from Maple Leaf Foods. It eventually killed more than twenty people. Since then, it had seemed like the province had to contend with a possible outbreak nearly every week. She couldn't exactly say a worldwide pandemic was in her comfort zone, but by 2020 she'd had two decades of experience working with outbreaks. She wasn't about to panic—and besides, nobody had yet guessed how big the outbreak was about to become. There was something about its potential, though, that did make Allen want to move fast. She called her colleagues, and by the end of the day they had a testing algorithm in place should anybody in Ontario turn up with symptoms.
  
  At the time, the full genomic sequence of SARS-CoV-2 didn't even exist. But Allen and her team knew the virus was similar enough to both MERS and SARS for them to make what was, essentially, a very educated scientific guess—one that could give them a jump-start on testing. About a week later, on Saturday, January 11, Chinese health authorities released the full sequence for SARS-CoV-2, confirming its striking similarity to the other coronaviruses (and, in particular, to two unnamed bat-derived coronaviruses). That same weekend, Allen's team completed their first test. The results were negative for the virus, and so too was every other test the team performed over the next week. Their ironically lucky strike-out record didn't stop the team from saying yes to testing every sample sent to the lab. If you were the on-call microbiologist during that time, you were constantly fielding calls, accepting samples. In what turned out to be a controversial decision, Allen decided to test everything she was asked to, no matter how unlikely it was to be SARS-CoV-2. As worry multiplied, she made it clear to anxiety-filled hospitals that she would never refuse a request. "It was a huge debate," she said of the policy. "People were worried we were making more of it than we needed to."
  
  There are countless ways a human body can get sick. Before the microscope was perfected in the 1600s, scientists tended to blame outbreaks on everything from social class to divine punishment to clouds of disease-laden air. To them, the idea that an imperceptible organism could invade a person's body and cause illness or even death would have sounded far more ludicrous than even their most bizarre theories. But the microscope literally opened a rich, new world to discovery—that of germs. Working in Berlin, Robert Koch discovered the first bacterium, bacillus anthracis, which causes anthrax, in 1876. In time, bacteria became classified as living, single-celled creatures that can cause deadly infections in their host. Bacteria cells are not so dissimilar to mammalian ones, although they are far more simplistic. Think of an air balloon that contains water, nutrients, and a single molecule of DNA. They can replicate on their own and cause harm by directly killing their human host's cells, or by triggering an immune response so severe it damages a person's body. Bacteria's long-awaited discovery led scientists to finally declare the cause of relatively common diseases such as tuberculosis, cholera, and syphilis. The cause of certain other prevalent and deadly diseases, like smallpox, however, remained a mystery. Scientists took sample after sample, but no bacteria could be found.
  
  Initially, they assumed such diseases must be caused by bacteria that were too tiny to be captured through the microscope. They were half-right. It wasn't until the 1930s, with the invention and development of the more powerful electron microscope, that they were able to finally detect the much smaller microbes. Unlike bacteria, viruses are not cells. They consist of a protein coat, called a capsid, inside which the virus stores its genetic material, which in turn carries the code for making new viruses. Many viruses may be deadly, but they lack one key thing: any of their own biochemical machinery to build more particles. In other words, they can't procreate on their own. Viruses overcome this by invading a host's cells and hijacking their machinery to transform them into virus-making factories. In the process, they usually kill the cell itself, either through nutrient depletion or the creation of a toxic environment. After this, sometimes the cell will burst, sending more virus particles into the body. Today, it's estimated that our immune system goes to war against tens of millions of germs every single day. Of them, viruses are the most ubiquitous: they're at least ten times more common than bacteria, and there are at least a hundred million different types. In fact, they are the most plentiful lifeform on Earth—and, every now and then, a new one comes along.
  
  After completing dozens of tests that identified other viruses and bacteria, Allen received Mubareka's sample. Also a clinician at Sunnybrook, she knew about the patient's symptoms and history, and like Mubareka, she suspected this sample would, finally, be a match. Allen ran the virus test only a few days after her twins' birthday, which was on January 16. After the sample was confirmed positive for SARS-CoV-2, she barely saw her family again for months. Her life became a blur of planning, testing, meeting, and troubleshooting—she was in charge of, or a key voice for, it all. During that time, additional leadership responsibilities were also heaped onto her plate: she became the executive lead for PHO's lab response and served as the inaugural medical director of the provincial diagnostic network housed at Ontario Health. From the beginning, Allen worked seven days a week, often for eighteen hours a day. It wasn't uncommon for her to be booked into a mind-boggling twenty-four meetings in a single day. If women had been historically relegated to the scientific sidelines during past pandemics, then it was clear to Allen things would be different this time. Every gender lined the Brady Bunch–style tiles of her virtual meetings, and many of the leaders she dealt with most frequently were women.
  
  When I spoke to Allen shortly after the six-month mark of the pandemic, she had just started taking one day off a week. Like Mubareka, she worried about her singular focus on work and felt guilty about being so unavailable to her family. In trying to explain her new-normal busyness, she picked a random day from her calendar, April 6. On that day, she led discussions on finding better processes around the province's prioritization and allocation of testing swabs; prepped for an urgent meeting with the premier's office; sat in on Ontario's weekly command table gathering, which assembles experts from across the province to discuss their concentrated approach to COVID-19; launched and met with another testing strategy panel to address what she saw as a lack of diversity in voices at the table; and helped plot a way to fix underserviced testing areas in Ontario's north—to name only a few things. An average day might include more, but rarely less. "So," she quipped, "it certainly hasn't been boring."