Debate over the origins of SARS-CoV-2, the virus that causes COVID-19, has reached a fever pitch in recent weeks. Back in March, the World Health Organization released the findings of a study concluding that it was most likely transmitted directly from animals to humans. Less than two months later, a group of prominent scientists publicly called for more serious consideration of the possibility the virus was leaked from a lab – a hypothesis previously dismissed as a conspiracy theory. Biden administration officials, including infectious disease expert Anthony Fauci, now also back further investigation.

Talk of further sleuthing prompted me and my colleagues to wonder: How do scientists determine the origins of a virus? And is that even possible with COVID-19?

For answers, we reached out to viral ecology expert Marilyn Roossinck of Penn State to walk us step by step through the clues and tools viral detectives use to trace viruses to their origins. It turns out it’s not quite as elementary as you might think.

Also today:

Vivian Lam

Assistant Health and Medicine Editor

The prevention of future pandemics requires examining viral family trees. Stockcrafter/iStock via Getty Images Plus

How virus detectives trace the origins of an outbreak – and why it’s so tricky

Marilyn J. Roossinck, Penn State

Bat hosts, lab leaks – tracing SARS-CoV-2 to its origins involves more than just tracking down patient zero.

Science + Technology

  • Study shows AI-generated fake reports fool experts

    Priyanka Ranade, University of Maryland, Baltimore County; Anupam Joshi, University of Maryland, Baltimore County; Tim Finin, University of Maryland, Baltimore County

    Bots flooding social media with fake news about politics is bad enough. Muddying the waters in such fields as cybersecurity and health care could put lives at risk.

  • Why are some mushrooms poisonous?

    Karen Hughes, University of Tennessee

    Poison can be a deadly defense that helps a mushroom make sure its spores are spread to new places to grow into baby mushrooms.

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