Danielle Anderson was working in what has become the world’s most notorious laboratory just weeks before the first known cases of COVID-19 emerged in central China. Yet, the Australian virologist still wonders what she missed.

An expert in bat-borne viruses, Anderson is the only foreign scientist to have undertaken research at the Wuhan Institute of Virology’s BSL-4 lab, the first in mainland China equipped to handle the planet’s deadliest pathogens. Her most recent stint ended in November 2019, giving Anderson an insider’s perspective on a place that’s become a flash point in the search for what caused the worst pandemic in a century.

The emergence of the coronavirus in the same city where institute scientists, clad head-to-toe in protective gear, study that exact family of viruses has stoked speculation that it might have leaked from the lab, possibly via an infected staffer or a contaminated object. China’s lack of transparency since the earliest days of the outbreak fueled those suspicions, which have been seized on by the U.S. That’s turned the quest to uncover the origins of the virus, critical for preventing future pandemics, into a geopolitical minefield.