Thread by @Ayjchan

On the pangolin story that is still drawing breath, "(Shi Zhengli, WIV) said that if the intermediate host was the pangolin.. it’s possible the virus jumped from bats to pangolins outside China.. smuggled in from other Asian nations, including India."
theguardian.com/world/2020/dec…

Thankfully, before scientists go on a wild goose chase to sample pangolins in India, David Robertson (U of Glasgow), who was also interviewed, said, “We’re fairly confident the pangolins have picked up their virus, presumably from horseshoe bats, after being imported into China.”

If any pangolins need to be investigated, I recommend starting with the Guangdong pangolins confiscated in March, 2019. This is the only batch of pangolins with a CoV that has a SARS2-like Spike RBD. Many questions remain re: the sample histories and data. biorxiv.org/content/10.110…

Closest virus relatives to SARS2 found in Yunnan province, China. No pangolin CoVs found in Malaysia for the past decade. Only 2 pangolin CoVs found in Guangdong and Guangxi province, China.

Their conclusion: let's look in South Asia, including India.

Have to knock on journalists a bit. Not the first time today, while reading news articles @nytimes @guardian noticed no links to the studies cited.
"Analysis the team published in October indicated that some were already capable of invading human cells..."
theguardian.com/world/2020/dec…

Not sure why SARS-like CoVs from nature being capable of infecting human cells is so surprising - WIV already published this in 2013: "bat SL-CoV-WIV1 can grow in human alveolar basal epithelial..." nature.com/articles/natur…

"ability of SL-CoV-WIV1 to use human ACE2.. suggests that direct bat-to-human infection is a plausible scenario"

And in 2015: "circulating bat CoV pools maintain 'poised' spike proteins that are capable of infecting humans without mutation or adaptation" nature.com/articles/nm.39…

Sep '19 paper: "proven potential of some SARSr-CoVs currently circulating in bats in southern China, to infect human cells, cause clinical signs in humanized mouse models.. infections that cannot be treated with monoclonal therapies effective against SARS" sciencedirect.com/science/articl…

In @guardian article, Shi also speculates that SARS2 could've been in intermediate hosts or humans “for a very long time”... in this scenario, where could a highly infectious SARS virus be circulating undetected prior to outbreak in Wuhan?

"1,596 residents were enrolled in the study from 2015 to 2017" in "Yunnan, Guangxi, and Guangdong, China, which are known for their high levels of wildlife biodiversity, active wildlife trade activity, and historic zoonotic disease emergence events"
sciencedirect.com/science/articl…

"participants were asked to provide a blood sample... and an oropharyngeal swab (stored in a cryotube with viral transport medium)."

The paper reported 0.6% seropositivity for SARS-CoVs, but doesn't report if any of the ~1,500 swabs had SARS-CoVs. sciencedirect.com/science/articl…

In essence, a multiyear (2015-2017) survey in rural communities most at risk of SARS virus exposure found very low seropositivity (0.6% rural; 2.7% people living near bat caves), and did not report detecting -any- SARS-related CoV in ~1,500 human samples. ncbi.nlm.nih.gov/pmc/articles/P…

In comparison, the first covid case in Singapore was confirmed on Jan 23; by Mar 16, 7 clusters (243 cases) of local transmission had been identified, even in a country where strong public health measures had been rapidly implemented from Jan 3 onwards. channelnewsasia.com/news/singapore…

Considering how fast this virus spreads, even with public health measures in place, not to mention if undetected + no measures taken, makes me question how likely it is that covid was already in other populous cities prior to the outbreak in Wuhan.

Similar situation in South Korea: first covid case confirmed Jan 20, "became the second most infected country after China by early March" despite again massive, rapid efforts by the South Korean government and people to contain the outbreak.
csis.org/analysis/timel…

Thailand & Japan are in the top three Wuhan air travel destinations:

Thailand first covid case confirmed on Jan 13
statnews.com/2020/01/13/wom…

Japan first covid case found on Jan 15, but patient symptoms began on Jan 3.
cidrap.umn.edu/news-perspecti…

Both had 100+ new daily cases by Mar.

Even if one speculates that a remotely located village was where the virus was pre-circulating+adapting/diversifying in animals/humans, how did sars2 break out only in Wuhan at first? Much more difficult to believe that sars2 originated as far away as India, Barcelona, or Italy.