The release of long-awaited surveillance data by the China CDC reveals that SARS-CoV-2 was indeed present at the Huanan Seafood Market in Wuhan at the onset of the global COVID-19 pandemic, shedding light on the initial epidemiological link to the market and highlighting the potential role of animal-to-human transmission, while addressing concerns over the laboratory leak hypothesis.

Understanding how the global COVID-19 pandemic emerged in late 2019 in Wuhan, China has been a subject of intense interest, given the concern that ongoing coronavirus research at the Wuhan Institute of Virology (WIV) could have enabled a laboratory leak of SARS-CoV-2. However, most of the initial COVID-19 cases were epidemiologically linked to Huanan Seafood Market (HSM), where animal-to-human transmission might have occurred. Consequently, the market was closed in December 2019 and the China CDC performed surveillance testing for the virus during January–March 2020. Now, their findings have been published.

In all, 73 of 923 environmental samples and 0 of 457 animal samples were PCR-positive for SARS-CoV-2. The positive environmental samples were primarily obtained from the sewer as well as a section of the market selling a range of animals and animal products. In addition, live virus was successfully cultured from three samples that were genomically identical to the initial human SARS-CoV-2 isolates. In further analysis for the presence of mammalian genes, >70 mammalian genera could be identified in >2% of the samples. The most common of these genes were human, but they also identified the presence of species of bats, raccoon dogs, and badgers known to be potential hosts of coronaviruses.

These findings are supplemented by a separate report prepared by the international team that discovered the raw metagenomic sequence data files for the environmental samples publicly posted on the GISAID database in March 2023. After first contacting China CDC researchers, this team performed an independent data analysis reported to the WHO. The highest frequency of DNA sequences from animal species susceptible to coronaviruses occurred in samples from the same market section where wildlife was sold — and where the highest frequency of environmental samples positive for SARS-CoV-2 was obtained. In one stall in this section, five samples were positive for SARS-CoV-2 and a sixth contained raccoon dog DNA and RNA with minimal human DNA, affirming a tight geographic localization between this animal and the virus.1

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References

  1. Crits-Christoph, A., Gangavarapu, K., Pekar, J. E., Moshiri, N., Singh, R., Joshua, L. ., I., Goldstein, S. A., Suchard, M. A., Popescu, S., Robertson, D. L., Lemey, P., Wertheim, J. O., Garry, R. F., Rasmussen, A. L., Andersen, K. G., Holmes, E. C., Rambaut, A., Worobey, M., & Débarre, F. (2023). Genetic evidence of susceptible wildlife in SARS-CoV-2 positive samples at the Huanan Wholesale Seafood Market, Wuhan: Analysis and interpretation of data released by the Chinese Center for Disease Control. Zenodo (CERN European Organization for Nuclear Research). https://doi.org/10.5281/zenodo.7754299

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