Flu has about one base pair RNA mutation between each viral generation (cell to cell), coronavirus's with rna the length of the current one aren't possible with

Flu has about one base pair RNA mutation between each viral generation (cell to cell), coronavirus's with rna the length of the current one aren't possible without an error correction mechanism, and as a result of having that they have about only one base pair mutation between each host transmission (person to person). I don't know the answer to your question, but it seems much harder with flu due to more rapid variation.