More than four years after the pandemic began, a source for COVID-19 still eludes scientists and public health officials. The mystery has given rise to a slew of hypotheses ranging from natural zoonotic transmission to lab leaks. But to get to the bottom and find the real source of the virus, you have to start with the evidence.

Alina Chan is a scientific advisor at the Broad Institute and the co-author of the book, Viral: The Search for the Origin of COVID-19. She and her co-author Matt Ridley follow one evidence thread to the next in order to get closer to the truth.

Alina joins Greg to chat about the two dominant hypotheses on COVID-19’s source, the challenges and methodology of identifying a virus’ origin, and why it’s crucial we find out where COVID-19 came from.

*unSILOed Podcast is produced by University FM.*

Episode Quotes:

The debate over studying high-risk pathogens

43:50: There are definitely people who think that all of this research should be banned, but I think that there should be a certain amount allowed to continue. Again, this sort of research, where there's actually any pandemic risk, constitute an extremely small fraction of virology. So, I would say, like, less than even a percent, maybe even less than that. So, most virology doesn't even concern animal viruses. And those that do often do not pose a risk to cause outbreaks in people. But there are these types of research projects that are now becoming more and more trendy around the world, following in the footsteps of U.S. leaders to take these pathogens that could cause outbreaks in people and study them in the labs. And it's unclear where the risk is because some of these labs are doing it at such low biosafety levels. Or is it because there are so many of these high-biosafety labs now, and the work is increasing, yet in these labs there's still room for human error.

Public vs. scientists

51:56: Your political affiliation doesn't determine anymore whether you think this virus was natural or came through a lab. I would say that the difference between the public and scientists is that scientists, especially experts, tend to lean on priors very heavily, as well as peer-reviewed literature.

Is the focus on avoiding retroactive blame or preventing future research constraints?

43:03: I think it's both. So, since then, and over the past few years, you've seen so many letters by virologists. Dozens of them have signed letters saying we are totally fine in the U.S. We do not need any more oversight or regulation. We are good at self-auditing and self-inspecting. We don't need any external oversight over our work. So, there's a clear fear amongst virologists that if this pandemic was started by a lab accident in Wuhan, they would become constrained as well, and that people would also perceive them to no longer just be the good guys but to be a source of risk and danger.

Why bats carry so many viruses

24:45: I think bats, aside from humans, are probably the most interesting mammalian species out there for virologists. It's because these bats have been found to carry so many different types of pathogens, many of which can jump into people. So, like Ebola, coronaviruses, both MERS and SARS were found to have come from reservoirs, for example, but they're quite similar to humans in the context that they live in large groups. So, you go into one of these caves, easily millions of bats in there, but actually, they're quite different. So, they can fly, and so their body has to adapt to handle that really high heat that happens when you're flapping your wings at such a high speed. And that is related to traits in bats that help them to coexist with so many of these viruses. So, these viruses, while they cause very severe diseases in people, in bats, they just live mostly in the gut and don't cause any severe disease. So, bats have this invulnerability in a sense to all these very dangerous pathogens.

Show Links:

Recommended Resources:

Guest Profile:

Faculty Profile at Broad Institute

Her Work:

Viral: The Search for the Origin of COVID-19

443. Uncovering COVID-19’s Origin with Alina Chan

unSILOed with Greg LaBlanc