A: The origin of the COVID-19 pandemic is still being unraveled.
The leading theory is that SARS-CoV-2 jumped naturally from bats to humans (possibly through an intermediate species), as other viruses have done for ages. The lab-leak theory – an accidental spill from a research lab – is the underdog. It’s far less likely but has not been ruled out. Politics and lack of transparency have clouded the discussion.
Nerdy Guest Dr. Chana Davis from Fueled by Science joins us today for the tl;dr on the origins of SARS-CoV-2:
COVID-19 is caused by the SARS-CoV-2 virus, a novel coronavirus. Experts think it originally came from bats because its genetic sequence is very similar to other bat coronaviruses. How exactly it got from bats to humans is unclear. 🦇
Most experts think that the SARS-CoV-2 virus likely jumped naturally to humans. Why? History! Animal viruses have brought us avian flus, SARS, MERS, AIDS, Ebola, and many more diseases. This is why experts often say that the next pandemic is a matter of when, not if. 😱
Coronaviruses are known to jump between species – both between bat species and from bats to other animals. For example, the coronavirus that caused MERS is thought to have originated in bats, then jumped to camels, which then infected humans. When viruses jump into new species, Franken-viruses often emerge thanks to raging viral mixer parties. Ménage à million anyone? 🦠
History is not the only reason to favor a natural origin. Evidence from early scientific sleuthing lines up with this theory. Twenty-seven of the first 41 COVID-19 patients identified were exposed to the same seafood market in Wuhan, where China’s CDC later found traces of the novel virus in 33 of 585 samples. While it’s still unclear where the other early cases came from, none have been clearly linked to the Wuhan Viral Institute.
Another strong argument for a natural origin is the “lottery” argument. For a virus, causing a pandemic is like winning the lottery. You can think of each coronavirus species, and each variant (or “scariant”) as a lottery ticket. In nature, there are tons of bats carrying coronaviruses, which are constantly mutating, as we know all too well. That’s a lot of lottery tickets. Every time humans come into close contact with infected animals or their waste, we give that virus a chance to win big.
Labs, by contrast, don’t hand out many “lottery tickets”. Scientists create very few novel viruses (it’s a lot of work!) and accidental infections are extremely rare.
Who do you think won the lottery? We place our bets on Mother Nature’s tickets.
Why does the lab-leak theory persist? It’s messy. First, we don’t have a “smoking gun” to tell us exactly how SARS-CoV-2 got from animals to humans. Second, past investigations were unable to formally rule out the lab-leak theory, largely due to limited data access. Last but not least, political agendas keep fueling the debate.
To truly crack this case, we’d need to find the family of bats, or intermediate animals, in which the SARS-CoV-2 virus happily hangs out – the natural “reservoir”. This is really hard. With other outbreaks it took months (SARS, MERS) or decades (HIV) to hunt down the source. For some viruses, like Ebola, the source remains unknown. Some crimes remain unsolved despite intensive investigations.🕵🏽♀️
As evolutionary biologist Dr. Joel Wertheim put it: “Not having answers to difficult scientific questions shouldn’t force us to default to conspiracy theories…It took scientists decades of research to find the chimpanzee host populations for the HIV/AIDS pandemic” (link to interview below).
Where does this leave us? Still sleuthing. We agree with 18 leading scientists in their letter to Science: “A proper investigation should be transparent, objective, data-driven, inclusive of broad expertise, subject to independent oversight, and responsibly managed to minimize the impact of conflicts of interest” (link below). 🔎
The frustratingly slow unraveling of this pandemic’s origins is a great reminder that science is a method, not a set of facts (link to post below). For now, the natural theory is the frontrunner, and the lab-leak remains the underdog. Although we are learning more each day, we may never crack this case.
Until then, don’t forget Nerdy Girl Lindsey’s first law: Extraordinary claims require extraordinary evidence (credit to Carl Sagan, link to post below).