A viral bioweapon has nearly 100% fatality rate. Otherwise, if you release it on your enemies, it goes pandemic and then kills your own people. Also wouldn't be nearly 99% match to a bat coronavirus collected in 2013 but, rather, heavily engineered.
There is a chance this was definitely a lab leak, however, but the question is from what lab considering that virus was exported to labs around the world.
You have two versions of the contagion. One that is mild but causes immunity to both. By releasing that one to your own population you protect them against the more aggressive version that you spread among the enemy.
There is a theory that the Chinese have a milder version of the new corona and that they sprayed it in Wuhan after the bad virus got out by mistake.
Then they isolated Wuhan from the rest of China while still keeping the international flights going out.
The problem here is that the original variant is not endemic in China but, rather, the United States. We really should strongly consider whether this route of attack against China is worthwhile.
The genomic data is very sparse, so maybe with more samples this will sort itself out and the type A cases will be shown to be monopolized by some particular region of China (one should expect Yunnan), but right now.. nope. America.
If this really is a lab leak, then I would bet on UNC Chapel Hill based on what evidence we currently have.
It could still have leaked from Wuhan, but the conditional probability chain there is pretty bizarre: leaks from Wuhan Institute of Virology --> Somehow travels to the US --> spreads back to Wuhan where it mutates into type B and we begin to notice it as it goes epidemic in Wuhan..
Parsimony alone, however, should lead us to strongly consider the possibility of a lab leak. The odds that we collected this virus in 2013, were experimenting on it in several labs around the world (Wuhan, UNC Chapel Hill, and -- I think -- that lab in Canada), and then it just coincidentally was that very virus that made the leap from bats to humans somehow far away from the habitat of those particular horseshoe bats (even if you want to assume it began in Wuhan).. LOL
I still don't understand how you come to an American origin.
Zhou et al. (7) recently reported a closely related bat coronavirus, with 96.2% sequence similarity to the human virus. We use this bat virus as an outgroup, resulting in the root of the network being placed in a cluster of lineages which we have labeled “A.” Overall, the network, as expected in an ongoing outbreak, shows ancestral viral genomes existing alongside their newly mutated daughter genomes.
There are two subclusters of A which are distinguished by the synonymous mutation T29095C. In the T-allele subcluster, four Chinese individuals (from the southern coastal Chinese province of Guangdong) carry the ancestral genome, while three Japanese and two American patients differ from it by a number of mutations. These American patients are reported to have had a history of residence in the presumed source of the outbreak in Wuhan. The C-allele subcluster sports relatively long mutational branches and includes five individuals from Wuhan, two of which are represented in the ancestral node, and eight other East Asians from China and adjacent countries. It is noteworthy that nearly half (15/33) of the types in this subcluster, however, are found outside East Asia, mainly in the United States and Australia.
Two derived network nodes are striking in terms of the number of individuals included in the nodal type and in mutational branches radiating from these nodes. We have labeled these phylogenetic clusters B and C.
