Let me speak to the second criticism (I'm not sure I fully understand the first one). The quote in context from the paper is: "there is no significant differen

Let me speak to the second criticism (I'm not sure I fully understand the first one). The quote in context from the paper is: "there is no significant difference between B.1.1.7 and non-B.1.1.7 viruses in total infectiousness predicted by our model" But "predicted by our model" is doing considerable work here, as the model doesn't take into account potential differences in what happens after someone is exposed to the virus, only what's measured in the study (viral shedding dynamics). So I think the critique of Prof Balloux is worth heeding: it would be a leap to conclude that alpha is definitely not more "infectious" than ancestral type when you take into account the broader meaning of "infectious." Even so, to my mind that places even more burden on demonstrating a biological mechanism. It also refutes a major claim in TFA and calls into question the methodology used to support that claim: "In China, they estimated the viral load of Delta to be 1,000 times higher than that of the original variant." But when you look at viral load specifically, as is done in the Ke et al paper, you find no difference at all. A few things could be going wrong here, but my money would be on some problem in how that 1000 factor was "estimated."