It is not yet clear exactly where the idea for the story of a lab leak originated but there was never any substantive evidence to support it. Nonetheless, over a short period of promotion by the United States it was actively taken up by the Australian government (ironically, with devastating long-term consequences for the Australian economy and the livelihoods of many Australian farmers), followed by partisan political commentators from a number of other countries.

The central hypothesis, which might better be stated as an allegation, was that SARS-CoV-2 had been deliberately engineered at the Wuhan Institute of Virology (WIV) as a result of unethical “gain of function” research and then, probably inadvertently, released to the public (amplified at the Huanan wet market) by a laboratory worker. From the beginning, the only “evidence” that was advanced in support of this claim was: (1) the proximity of the laboratory to the market; (2) assertions that features of the SARS-CoV-2 genome that contribute to pathogenicity and transmission (for example, the presence of a furin cleavage site, and binding to human ACE2 receptors) must have been inserted deliberately; (3) that these gain of function studies may have been done with malign intent; and (4) allegations that the Chinese authorities refused to provide full access to laboratory records in response to demands for accountability, supposedly indicating the presence of a cover-up.

The first claim is probably spurious. The WIV is located at least 20 kilometres from the Huanan wet market, the agreed epicentre of the Wuhan outbreak. It is an international leader in bat virus research, including with SARS-related coronaviruses (SARSr-CoV), and has published extensively, but no evidence has been presented that SARS-CoV-2 was ever studied at the WIV prior to the emergence of disease at the Huanan wet market in December 2019, nor that there were other unpublished similar viruses isolated in the laboratory. Laboratory leaks can happen, generally when viruses have been isolated in tissue culture where viral loads are very high, rather than directly from clinical samples. The SARSr-CoV sequenced at the WIV, RaTG13 (collected in 2013), is one of the viruses most closely related to SARS-CoV-2 but was only available as a viral sequence and not as a viral isolate. Research and public health laboratories, the latter managed through the Chinese Center for Disease Control (CDC) system are found in provinces and many large cities in China, where research into important and dangerous disease is well supported. One might speculate that wherever an urban outbreak in China might occur it would be likely that a viral laboratory might be found reasonably nearby. In Wuhan, in addition to the research focused WIV, there are Wuhan CDC and Hubei Province CDC public health laboratories as well as university and veterinary laboratories. This is similar to other major cities in China.

The second claim has now been comprehensively disproved in work by scientists from Australia and elsewhere, which have shown that the SARS-CoV-2 features that allow ready human transmission can all arise by natural evolutionary processes in animals (Andersen et al., 2020; Dwyer 2022; Holmes et al. 2021). Through meticulous analysis of the viral sequence these studies have identified no evidence of human intervention, through genetic modification, including addition or deletion of sequences. In addition, they have shown that all relevant features of the virus occur in nature in settings that make a natural evolutionary process both feasible and plausible. Coronavirus genomic similarities in bats (and pangolins), the characteristics of bat SARSr-CoV, the known coronavirus genomic plasticity, the recent historical emergence of other human and animal coronaviruses, and the complete lack of evidence of an actual laboratory leak means that in vivo coronavirus recombination or mutation in host and intermediate animals are overwhelmingly likely as the driver of human SARS-CoV- 2 (Andersen, et al. 2020; Holmes, et al. 2021).

The third claim has no evidence or credible basis, and indeed, no attempt has even been made to provide any relevant data to support it. The fourth claim—that Chinese authorities have failed to provide access to all relevant data to interested parties—remains open and would require further evidence to be resolved. However, it is noted that a forensic investigation of the WIV was not within the terms of reference of the WHO Study Group and, despite calls from some parties, there has been no formal process within which such an investigation has been required. Nonetheless, recently published analysis by American and European researchers of metagenomic sequencing data publicly available on GISAID has demonstrated the co-occurrence of SARS-CoV-2 and the genetic material of susceptible wildlife in environmental samples from the Huanan wet market during the start of the COVID-19 pandemic, indicating strongly that the vector at this location was an animal (possibly a racoon dog) rather than a human. These findings mitigate against the hypothesis that the virus was introduced to the market through a human host (Liu et al., 2023a; SAGO 2023).

Perhaps predicably, the raising of unsupported allegations against Chinese scientists in a context considered by the Chinese government to be scurrilous and unfair directly undermined the possibility of a much-needed collaborative investigation into the actual causes of the unfolding disaster. Instead, the Chinese countered, unhelpfully, with unfounded allegations of their own, suggesting that the virus could have been deliberately engineered in the United States and released as an act of sabotage by an American undercover agent during the military games which had been held in Wuhan a few months before the index super-spreader event. It should be noted that the U.S.A National Intelligence Council (NIC) has given an updated assessment, with varying levels of confidence, of the origins of SARS-CoV-2: China did not develop SARS-CoV-2 as a biological weapon, SARS-CoV-2 had not been genetically engineered; Chinese authorities were not aware of SARS-CoV-2 before the initial outbreak; and that that infection was most likely caused by natural exposure to an animal infected with it or a close progenitor (Office of the Director of National Intelligence, 2023).

While the American, Australian, and Chinese claims were all theoretically possible, as mentioned, they have now been discredited as there are no good data to support them, and we have to look elsewhere for the “origins” of the new virus. Luckily, here, the evidence is plentiful. A substantial body of knowledge, supported by a great deal of data, favours the original hypothesis of most informed experts: that the emergence of the SARS-CoV-2 virus occurred, like its predecessors, as a result of the well-documented processes of mutation within animal reservoirs followed by cross-species transmission to humans. This is a process that has occurred many times in the past with coronaviruses and other pathogens and, as noted, was long expected by scientists and other experts in the field (Bloom 2021; Ferreira, et al. 2021; Slingenbergh, et al. 2004).

The continuing, well characterized mutations of the virus support this understanding and underline the perverse nature of the allegations against the Wuhan scientists. While the currently circulating variants are significantly different from the original Wuhan version, incorporating up to a hundred or more novel mutations, it is now universally accepted that this is the result of the remarkable ability of this family of viruses to evolve. Indeed, no one has claimed that the new variants of the virus (such as Alpha, Beta, Delta, Omicron etc.), which variably emerged from the United States, Europe, South Africa, India, and South America, were deliberately engineered in a laboratory. If it is possible to accept such a natural process of mutation now, the likely role of similar processes before the appearance of the “Wuhan strain” became known should be all too apparent.