Reason 1: The lab's samples don't match the new coronavirus
The WIV houses China's only Biosafety-level-4 laboratory. Scientists study the most dangerous and infectious microbes known to humankind in these types of facilities. Some of the institute's researchers, including virologist Shi Zhengli, have collected, sampled, and studied coronaviruses that circulate Chinese bats ... After her team sequenced the COVID-19 virus, Shi told Scientific American that she quickly checked her laboratory's record from the past few years to check for accidents, especially during disposal. Then she cross-referenced the new coronavirus' genome with the genetic information of other bat coronaviruses her team had collected. They didn't match. Mazet has met and worked with Shi through PREDICT, a pandemic early-warning program started by the US Agency for International Development. "I've spoken to her recently," Mazet said of Shi. "She is absolutely positive that she had never identified this virus prior to the outbreak happening."
Reason 2: The lab implements rigorous safety protocols
... Mazet said Shi's work in the lab and in the field was above reproach. "In the field, they wear extreme personal protective equipment, including multiple layers of gloves, eye protection, full body suits, and masks," she said. Samples collected from bats, Mazet added, get immediately split between some vials that contain chemicals that deactivate the virus, and other containers that leave the virus alive. All samples are then dunked into liquid nitrogen on the spot, which freezes them, then the vials are disinfected and transported to the lab. There, scientists wearing personal protective equipment (PPE) unload them into a freezer set to minus 80 degrees Celsius. When the samples are studied later, researchers only use the deactivated, non-infectious ones, Mazet said, adding that the vials with viable virus are locked down in a special area.
Reason 3: The coronavirus is the latest in a long line of zoonotic disease outbreaks
Rather than a leak, the coronavirus is more likely the latest disease to have jumped from an animal host to humans, experts say. This type of cross-species hop, called a spillover event, also led to outbreaks of Ebola and SARS ... Three out of every four emerging infectious diseases come to us from other species; these pathogens are known as zoonotic diseases. The coronavirus is the seventh zoonotic virus to have spilled over into people in the last century.
Reason 4: Everyday people are more likely to get infected than researchers who wear protection
The caves and wild habitats in which samples get collected from bats are dangerous places for people, since humans can be exposed to the live viruses circulating in the animals, Mazet said. Shi's researchers navigate those caves in full PPE; but tourists, hunters, poachers, and other people who rely on animals in some capacity for food or trade wander into such places less protected.
