Origin of COVID-19?

Scientists still haven't determined conclusively where SARS-CoV-2 originated. This question can be answered in one of two ways:

1. What animal species was the original host of this virus? This approach relies on an understanding of zoonotic diseases (diseases that originate in animals and then spill over into humans). Original theories pointed to a live-animal market in Wuhan, China, but the research is still inconclusive. What does seem certain is that the reservoir host was likely a bat. A second theory is that the virus was created in and escaped from a lab.
2. How did the virus evolve through mutations and natural selection so that it could infect humans? This second approach relies on our understanding of evolution and natural selection.

Investigation of Origins of SARS-COV2

This is an ongoing investigation and to understand it, I turned to peer-reviewed journals and found this article The origins of SARS-CoV-2: A critical review , published in the Journal Cell. It is co-authored by long list of scientists from different universities, institutions, countries who have been researching viruses and their origins for many decades, Here is a summary of what they say in this article:

- There have been several different coronaviruses that have spilled over from animal populations into humans
  - SARS-CoV-1 in 2002, 2003
  - MERS in 2012
- In the case of SARS CoV-1, it was associated with ''Wet Markets'' (where live, exotic animals are sold primarily for food)
- The closest relative for SARS- CoV2 are viruses that are found in bats in Yunnan Province in China.
- There is significant genetic difference between these ''wild'' viruses and SARS-CoV-2.
- They have not found a bat reservoir or intermediate animal host for SARS-CoV-2 to date.
- This is the case for nearly all spillover events including Ebola, hepatitis C, polio - the original animal populations have never been identified.
- The first cases of SARS-CoV-2 were in Wuhan, China which is 100's of miles from Yunnan.
- Wuhan was the epicenter of the 2019 outbreak, with the majority of those cases showing up around one particular wet market (Huanan Market)
- This market (and others) trade in wild animals.
- SARS-CoV-2 was detected in environmental samples after the market was closed down.

- The Wuhan Institute of Virology (WIV) stores samples of many different viruses, including those from bats, and coronaviruses - but very different genetically from SARS-CoV-2.
- The samples at WIV lack a key characteristic of SARS-CoV-2 ( the furin cleavage site)
- The concern is that they may have done ''gain of function'' research and had an accidental release.
- Gain of function research is done with well studied viruses, not novel viruses. If this had happened, it would be expected that the result would be similar to existing coronaviruses, which SARS-CoV-2 is not.
- This type of research is done with mice, but early SARS-CoV-2 was unable to infect mice consistently.

They conclude, that the most likely origin was from an animal population, with bats being the most likely.

Update:

The Huanan market was the epicenter of SARS-CoV-2 emergence

Here is a link to an article that is going to be published that follows up on the above research. The researchers did some clever investigation of the data showing the locations of the earliest cases of COVID-19. They then matched those to the genetic sequence of the earliest versions of the virus and were able to locate the Hunan Market as the epicenter of the earliest viral infections.

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