Origin of SARS-CoV-2

Discovering the origin of SARS-CoV-2 is infinitely less urgent than dealing with it effectively now that it is here, but still of scientific interest. SARS-CoV-2 is closely related to certain coronaviruses that occur naturally in Southeast Asian bats and pangolins. (Pangolins are scaly anteaters heavily trafficked in China for food.) No one yet knows exactly how the virus jumped to humans. There have been two lines of thought.

Lab-origin hypothesis

This rests on proximity. SARS-CoV-2 surfaced in a city that is home to the Wuhan Institute of Virology where researchers have long studied bat coronaviruses. Lab accidents can happen, and China has not completely cooperated with attempts to investigate this possibility. Some persons have even suggested that SARS-CoV-2 was created in a lab. However, the genetic sequences of SARS-CoV-2 essentially rule out deliberate engineering of any previously known coronaviruses (1). There is still no evidence for a lab leak or genetic engineering of this virus.

Natural-origin hypothesis

This rests on precedent. Influenza, Ebola, HIV, and the coronaviruses that cause SARS and MERS are just a few of the many viruses that have jumped naturally from other animals to humans without any laboratory tinkering. Along with bats, Malayan pangolins (Manis javanica) are a natural reservoir of SARS-CoV-2-like coronaviruses (3,4,6,7). Infected animals--or infected animal traders--could have brought SARS-CoV-2 to Wuhan food markets. Proving ease of cross-species infection, multiple other species of animals have become infected with SARS-CoV-2 from humans, both naturally and experimentally (2,5). Natural origin from bats, pangolins, or some other animal is not proven but highly plausible.

Conclusion

Based on what is known so far, infectious disease experts today favor the natural-origin hypothesis (3). REFERENCES

1. Cohen J. Call of the wild: Why most scientists say it's unlikely that SARS-CoV-2 originated from a "lab leak." Science 373; 3 September 2021;1072-7.

2. do Vale B et al. Bats, pangolins, minks and other animals - villains or victims of SARS-CoV-2? Vet Res Commun 2021 Feb;45(1):1-19. doi: 10.1007/s11259-021-09787-2.Epub 2021 Jan 19.

3. Holmes EC et al. The origins of SARS-CoV-2: A critical review. Cell.2021 Aug 19 doi: 10.1016/j.cell.2021.08.017 [Epub ahead of print]

4. Lam TT et al. Identifying SARS-CoV-2-related coronaviruses in Malayan pangolins. Nature 2020 Jul;583(7815):282-285. doi: 10.1038/s41586-020-2169-0. Epub 2020 Mar 26.

5. Mahdy MAA, Younis W, Ewaida Z. An Overview of SARS-CoV-2 and Animal Infection. Front Vet Sci 2020 Dec 11;7:596391. doi: 10.3389/fvets.2020.596391.eCollection 2020.

6. Xiao K et al. Isolation of SARS-CoV-2-related coronavirus from Malayan pangolins. Nature 2020 Jul;583(7815):286-289. doi: 10.1038/s41586-020-2313-x.Epub 2020 May 7.

7. Zhang T, Wu Q, Zhang Z. Probable Pangolin Origin of SARS-CoV-2 Associated with the COVID-19 Outbreak. Curr Biol 2020 Apr 6;30(7):1346-1351.e2.doi: 10.1016/j.cub.2020.03.022. Epub 2020 Mar 19.