Originally published 2020-02-15.
No, snakes did not spread the new coronavirus to people. In January 2020, a team of Chinese researchers suggested that two snake species sold in Wuhan might be the animal source of the virus we now call SARS-CoV-2. Within days, other virologists rejected the idea, and nothing found since has supported it. The virus behaves like a mammal virus, and its closest known relatives live in bats.
The snake theory is still worth understanding. It shows how quickly an early, untested paper can travel around the world, and why scientists treat a single computer analysis with caution until real animals and real samples back it up.
What the snake study actually claimed
The paper was led by Wei Ji, a microbiologist at Peking University Health Science Center, and appeared in the Journal of Medical Virology on 22 January 2020. At that point the outbreak was only a few weeks old, the virus was still known by its provisional name 2019-nCoV, and the world was hungry for any clue about where it came from.
The team did not test any snakes. Instead, they looked at "codon usage": the small preferences every organism and virus shows in how it spells out proteins in its genetic code. The idea is that a virus living for a long time inside one host may gradually drift toward that host's spelling habits. The researchers compared the new virus with possible hosts including bats, hedgehogs, pangolins, chickens, humans and snakes.
The closest match, they reported, was with two snakes: the many-banded krait (Bungarus multicinctus) and the Chinese cobra (Naja atra). Both are venomous species found in southern China, and snakes had been reported on sale at the Huanan seafood market in Wuhan, where many of the earliest patients had worked or shopped. Snakes also eat bats in the wild, so the authors sketched a chain from bats to snakes to people.
Casanowe/Getty Images
The story was irresistible to headline writers. A cobra is a far more dramatic villain than a small mammal, and within a day or two the claim was being repeated as if it were settled.
Why virologists rejected it so quickly
Experts outside the study raised three main problems, as Scientific American reported at the time.
No coronavirus had been found in snakes. Paulo Eduardo Brandão of the University of São Paulo pointed out that there was no consistent evidence of coronaviruses infecting anything other than mammals and birds. Cold-blooded reptiles have very different body temperatures and cell receptors.
Codon usage is a weak clue. David Robertson, a virologist at the University of Glasgow, said that "nothing supports snakes being involved." A brief stop in an intermediate host would not reshape a virus's genetic spelling in any measurable way; that kind of drift takes a very long time.
The family tree pointed elsewhere. The genome of the new virus was already known to be closely related to SARS-like coronaviruses collected from bats in China. Cui Jie of the Pasteur Institute of Shanghai, whose team had sampled such bat viruses in Yunnan, put it bluntly: "Clearly this 2019-nCoV is a mammalian virus."
In other words, the study measured something real, but the measurement could not carry the weight of the conclusion. That is a common pattern in the first weeks of any outbreak, when fast preprints and rapid papers arrive before the slower, more reliable evidence.
How coronaviruses jump from animals to people
Coronaviruses are a large family. Several cause ordinary colds, while a few have caused serious disease. Two earlier ones set the pattern scientists expected this time:
- SARS (2002–2004) is thought to have started in bats and reached people through masked palm civets sold in markets in southern China.
- MERS, first identified in 2012, also has bat relatives but spreads to humans mainly from dromedary camels in the Middle East.
Both are zoonoses: diseases that cross from animals into humans. A spillover usually needs repeated close contact, the right receptor on human cells, and a virus that can adapt well enough to spread from person to person afterwards. Crowded markets where many live mammals are kept together, slaughtered and sold provide exactly those conditions.
The name "corona" comes from the crown-like fringe of spike proteins visible around the virus particle under an electron microscope. Those spikes are what latch onto cells, and for SARS-CoV-2 the key target is a receptor called ACE2, which is found in many mammals.
What we know about the origin today
Years of research have narrowed the field, although the full answer is still debated. According to the summary of evidence on Wikipedia's origin of SARS-CoV-2 page, the closest known relatives of the virus are bat coronaviruses such as RaTG13, from Yunnan in China, and BANAL-52, found in horseshoe bats in northern Laos. Neither is a direct ancestor, but together they place the virus firmly in the bat branch of the family.
Possible intermediate hosts that have been studied include pangolins, civets and raccoon dogs. Swab data from the Huanan market, released in 2023, showed raccoon dog genetic material in the same stalls that tested positive for the virus. That does not prove raccoon dogs were infected, but it strengthened the case that live mammals at the market were involved.
A WHO-convened study in 2021 judged spillover from animals the most likely route. The WHO's later scientific advisory group (SAGO) reached a similar view in 2025, while noting that a laboratory accident could not be fully ruled out because key data from Wuhan had not been shared. Some governments and intelligence agencies favour the lab-leak explanation, and the question remains politically charged. Snakes, however, play no part in any of the serious scenarios still being discussed.
Myths and lessons from the snake scare
Myth: "Scientists said snakes caused COVID." One team proposed it as a hypothesis based on indirect data. Most of their colleagues disagreed immediately, and the idea never gained support.
Myth: "If it was published, it must be true." Peer review checks that a paper is reasonable, not that its conclusions are final. Big claims need independent confirmation, ideally from several kinds of evidence.
Myth: "The origin question has been solved." It has not. Most evidence points to a natural spillover involving mammals, but the exact animal and route have not been confirmed.
When this story first spread, there was no vaccine or specific treatment for the new disease. Vaccines were authorised from December 2020 onward, and treatments followed. If you have questions about your own risk or vaccination, talk to a doctor.
The broader lesson still stands. Trade in live wild animals, mixed together in crowded markets, gives viruses the chances they need to find new hosts. Reducing that contact, along with better surveillance of animal viruses, is one of the most practical ways to make the next pandemic less likely.
Sources: Ji W. et al., Journal of Medical Virology, January 2020; Scientific American: Some Scientists Skeptical about Snakes Spreading New Virus in China; Wikipedia: Origin of SARS-CoV-2; CDC: SARS; CDC: MERS. Photo credit: Casanowe/Getty Images.
COMMENTS