There's a lot of posts concerned about hypermutating leading to more dangerous strains. Ignoring the actual efficacy of the drug itself (I'm still reading the article), this is a pretty minor concern. The actual mutation rate of influenza is so high that raising it further doesn't actually make it any more likely to be dangerous, since mutants are selected for incredibly quickly already.

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Rough math:

Influenza is around ~14,000 base pairs long

mutation rate is around 1/1000 +/- an order of magnitude

there's around 100-200 virions per cell (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4947482/)

iirc there's 10^10 epithelial cells in the human lung, roughly

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so, you're looking at (10^10 * 10^2) = ~10^12 viral particles being created during an infection

with a mutation rate of ~10^-3.5, you're looking at 10^8.5 mutations. The influenza genome is 10^4 bp long

Point being, any immediate (i.e. single change) mutation in influenza will probably appear during a given infection at some point. These are, in practical terms, usually very minor changes to viral function if they do anything at all.

When you start looking at all possible double mutations, or n number of specific mutations on the starting strand in general, the odds of any particular one appearing are 1/14,000^n

So even if there was one possible mutant that only took 4 or 5 mutations to show up, you'd need 10^(4*4)

There's 10^31 viral particles on earth. If all of these were influenza, for any possible mutation that would be dangerous to appear in a single infection, it'd have to be <7 or 8 base pairs long before you'd have reasonable odds of it showing up.