Did Chinese Scientists Experiment With 'COVID-Like' Virus That Killed 100% Of Mice?

A study about the research was uploaded to the bioRxiv servers.

Published Jan 18, 2024

Updated Jan 19, 2024
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Image Via Getty Images

Key Facts:

  • Chinese researchers did conduct an experiment using a coronavirus that they found had 100% lethality in mice. However, the scientists did not "create" the virus, and it did not infect any humans.
  • Since the study has a small sample size and has not yet gone through the rigorous process of peer review, it is unreasonable to make assumptions about what the results of the study would mean for a larger population.
  • The main concern from scientists revolved around whether the study was worth conducting in the first place, given the inherent risk of the research. Ensuring that research is conducted safely and responsibly has been a major talking point in the field since the start of the COVID-19 pandemic.

On Jan. 4, 2024, a preprinted study was uploaded to the bioRxiv (Bio-Archive) servers by a group of Chinese researchers at the Beijing University of Chemical Technology. The paper, which had not yet gone through the peer-review process, describes a study that tested the lethality of a coronavirus on mice. The virus was genetically modified to more accurately study how diseases affect humans. According to the study, all of the mice injected with an active version of the virus died within eight days of infection.

The study was shared by scientists on the X platform (formerly known as Twitter) who debated the merits of conducting the research and its findings.

With the study's spread on social media, tabloids like The Daily Mail and the New York Post also picked it up, attaching fear-mongering headlines to the story, claiming among things that the researchers had created the virus. That was not true.

Below, we break down some of the key rumors.

First: The preprint and the study are real. During the COVID-19 pandemic, Bio-Archive became a tool by which researchers could quickly share information and breakthroughs with their colleagues without going through the long and laborious academic publishing process. It's a trustworthy source; however, because papers uploaded to the site have not been peer-reviewed, scientific findings need to be taken somewhat with a grain of salt.

Second: The virus used in the experiment is not a "new, mutated strain of COVID," as claimed in The New York Post's headline about the study. Coronaviruses, including SARS-CoV-2, the virus that causes COVID-19, are a family of viruses that share similar structures. The specific coronavirus used in the study, GX_P2V, was isolated from a pangolin coronavirus in 2017. The most accurate comparison might be to call SARS-CoV-2 and GX_P2V "cousins."

Third: The virus mutated from its original isolate, but it is a bit unfair to claim that the scientists "created" the virus. Since coronaviruses (and viruses in general) are known to rapidly mutate their genetic instructions, it is unsurprising that the virus used in the study mutated from the time it was isolated. In the paper (and in prior research by the same group), the researchers note that this particular variant of GX_P2V contained the mutation because it had better adapted to the cell cultures in which it was grown.

Fourth: The study was very small. Because you can't just inject someone on the street with a virus you know practically nothing about, researchers used lab mice instead. These mice had been genetically modified to contain the human proteins that SARS-CoV-2 uses to get into cells. The researchers used just 12 of these mice to study the lethality of the virus, and only four were injected with the live virus, all of which died. While this is indeed a 100% rate of lethality, there is simply not enough data about the virus to panic.

Fifth: At least two researchers did have former ties to the Chinese military, as claimed by The Daily Mail. This was a point that many on social media made, suggesting that the Chinese military was building a bio-weapon that it could use to decimate its political enemies.

The research was conducted by a team including Tong Yigang, a professor who formerly studied and taught at the Academy of Military Medical Sciences, part of the army's research division. Tong is not currently affiliated with that institution. Another professor involved in the study, Song Lihua, also completed a PhD at the Academy of Military Medical Sciences but has not been affiliated with the military since 2006. Snopes could not find other evidence confirming or denying possible connections to the Chinese military.

What most people, virologists and conspiracy theorists alike, were concerned about was the rationale for performing the study. There are two potential explanations for the origins of the COVID-19 pandemic: the zoonotic transmission hypothesis, meaning that an infected animal transmitted the disease to patient zero, and the lab leak hypothesis, meaning that safety protocols in a lab containing the pathogen were not followed effectively and the coronavirus infected patient zero from there.

Unfortunately, neither can be completely ruled out. Most, but not all, scientists and governmental agencies accept the animal-to-human hypothesis, but we will likely never know the true origins of the virus that causes COVID-19.

Nonetheless, in the wake of the pandemic, virologists have been investigating safety procedures to ensure that their research never becomes a threat to the general public.

The main critique focuses on a style of experimentation called "gain-of-function" research, where researchers learn about a virus by studying how its genetic makeup changes over time. Oftentimes, gain-of-function studies involve making the virus more potent and infectious, sometimes intentionally and sometimes not. Given the potential of the lab leak hypothesis as an origin for COVID-19, research deemed to be gain-of-function research has come under heavy scrutiny by both politicians and virologists who want to ensure public safety.

Figures like Francois Balloux, the director of University College London's Genetics Institute, criticized the researchers on X for not considering whether the potential findings were worth the risks of conducting the study.

Others called the study a dangerous misuse of gain-of-function research. On ScienceCast, an open-source forum used by scientists to share ideas and discuss their work, Song Lihua defended the paper:

"There have been unfriendly folks trying to misinterpret our work as gain-of-function research. Let me be clear – that is not the case. What we've done is simply tested a passaged virus mutant, nothing more. The ACE2 humanized mice used in our experiments are unique and do not exist in nature. The outcomes from these tests cannot be applicable to humans."

Snopes reached out to Francois Balloux and other experts in the field for comment. We will update this story with additional information as we receive it.


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This story was updated to add additional information provided by a researcher involved in the study, professor Song Lihua.

Jack Izzo is a Chicago-based journalist and two-time "Jeopardy!" alumnus.