wuhan lab
There are two main theories for SARS-CoV-2's origin. One maintains that the virus originated in bats, and then jumped to humans, most likely via an intermediate host species. The other states that the virus originated in a lab, but then accidentally escaped, perhaps due to inadequate safety protocols.

It should be noted that there are two slightly different versions of the latter, "lab leak" theory. One says the virus that escaped was of wholly natural origin; the other says it had been genetically engineered beforehand. In the diagram below, A corresponds to the first version of the lab leak theory and C corresponds to the second; B corresponds to the natural origin theory:

covid bat
The lab leak theory, you'll recall, was initially dismissed as a "conspiracy" - even though the location of the first outbreak (in proximity to the Wuhan Institute of Virology) suggested it was by no means implausible.

In September of 2019, Twitter suspended the Chinese virologist Li-Meng Yan after she claimed that SARS-CoV-2 was manufactured in a laboratory and accused the Chinese government of covering up evidence. (Dr. Yan subsequently fled to the United States over concerns for her safety.)

In February of 2020, 27 scientists wrote a letter to The Lancet, claiming studies "overwhelmingly conclude that this coronavirus originated in wildlife". The authors stated, "We stand together to strongly condemn conspiracy theories suggesting that COVID-19 does not have a natural origin."

In May of 2020, Anthony Fauci told National Geographic that the scientific evidence is "very, very strongly leaning toward this could not have been artificially or deliberately manipulated".

In June of 2020, Peter Daszak - organiser of the Lancet letter - wrote an op-ed for the Guardian. He again referred to proponents of the lab leak theory as "conspiracy theorists", and claimed that his own work "firmly concludes that COVID-19 originated in bats". (Daszak has actually funded gain-of-function research at the Wuhan Institute of Virology, and was the subject of 2015 news item in the journal Nature entitled 'Engineered bat virus stirs debate over risky research'.)

Even today, the Wikipedia page for "COVID-19 misinformation" says the lab leak theory is based on "unfounded speculation and conspiracy theories".
wikipedia covid-19
Yet over the last few months, the lab leak theory has entered the mainstream. Now leading scientists are calling for a new investigation into the origins of COVID-19. On May 14th, 18 scientists - including names from Harvard, MIT and Stanford - wrote a letter to the journal Science: "Investigate the origins of COVID-19."

The authors note, "Theories of accidental release from a lab and zoonotic spillover both remain viable." And they argue that "the two theories were not given balanced consideration" in the WHO's heavily-criticised investigation earlier this year.

The authors go on to state, "We must take hypotheses about both natural and laboratory spillovers seriously until we have sufficient data." And they say that a proper investigation "should be transparent, objective, data-driven, inclusive of broad expertise, subject to independent oversight, and responsibly managed to minimize the impact of conflicts of interest."

The origin of COVID-19 obviously remains an open-question. But the fact that a reasonable theory was dismissed as a "conspiracy" by many scientists and much of the mainstream press does not bode well for our ability to tackle future pandemics.

Stop Press: The editorial board of the Washington Post has called for a proper investigation into the lab leak theory.