The fact check does provide a good overview.
From the link:
>>>Baric [a professor in epidemiology, microbiology and immunology at the University of North Carolina] has said he thought the virus came from bats in southern China, perhaps directly or possibly via an intermediate host, and that he suspected the disease evolved in humans over time without being noticed. Eventually a person carried it to Wuhan “and the pandemic took off,” Baric told
New York magazine in January.<<<
That's the scenario I keep wondering about. Perhaps the virus was circulating in humans for some time in a region with lower population density and some local acquired immunity, and researchers from the Wuhan Institute were infected when they traveled to the region(s) where the bat viruses are common, bringing it back to Wuhan where it took off.
I had started wondering about this a while back when I ran across this article from 2018:
>>>Our study provides the first serological evidence of likely human infection by bat SARSr-CoVs or, potentially, related viruses. The lack of prior exposure to SARS patients by the people surveyed, their lack of prior travel to areas heavily affected by SARS during the outbreak, and the rapid decline of detectable antibodies to SARS-CoV in recovered patients within 2–3 years after infection strongly suggests that positive serology obtained in this study is not due to prior infection with SARS-CoV (Wu et al.
2007). The 2.7% seropositivity for the high risk group of residents living in close proximity to bat colonies suggests that spillover is a relatively rare event, however this depends on how long antibodies persist in people, since other individuals may have been exposed and antibodies waned. During questioning, none of the 6 seropositive subjects could recall any clinical symptoms in the past 12 months, suggesting that their bat SARSr-CoV infection either occurred before the time of sampling, or that infections were subclinical or caused only mild symptoms. Our previous work based on cellular and humanized mouse infection studies suggest that these viruses are less virulent than SARS-CoV (Ge et al.
2013; Menachery et al.
2016; Yang et al.
2016). Masked palm civets appeared to play a role as intermediate hosts of SARS-CoV in the 2002–2003 outbreak (Guan et al.
2003). However, considering that these individuals have a high chance of direct exposure to bat secretion in their villages, this study further supports the notion that some bat SARSr-CoVs are able to directly infect humans without intermediate hosts, as suggested by receptor entry and animal infection studies (Menachery et al.
2016).<<<
www.ncbi.nlm.nih.gov
I noticed that Baric and Daszak (paper above) appear to be two of the U.S. researchers most closely involved in coronavirus research in China. For example, Baric is an author for this paper:
Ralph Baric, Vineet Menachery and colleagues characterize a SARS-like coronavirus circulating in Chinese horseshoe bats to determine its potential to infect primary human airway epithelial cells, cause disease in mice and respond to available therapeutics.
www.nature.com
However, it appears to me that Daszak has consistently asserted that the lab leak theory is implausible, whereas Baric signed the letter published in Science to the effect that the lab origin theory cannot be ruled out.
At the risk of derailing this thread with politics, it is somewhat ironic that the NIH (under Trump) lifted the ban on funding for gain-of-function research in 2017:
>>>The National Institutes of Health
recently announced it would renew funding research enabling scientists to alter pathogens to make them more dangerous,
raising questions about whether the Trump administration had opened the door to a potential
pandemic.<<<
The National Institutes of Health recently announced it would renew funding research enabling scientists to alter pathogens to make them…
healthjournalism.org
