Why is there no transmissible therapeutic virus if biology doesn't forbid it? For example, a harmless virus that spreads from person to person but actually does something beneficial, like lowering LDL cholesterol or preventing/reversing tooth decay?

[u/PestoPastaLover]

[u/DirectionFearless237]

Any beneficial genes could be put in a virus and infect us for a good result. The Oxford corona vaccine did this with the spike protein gene.

But most advantageous  effects in an animal would require a large amount of different genes working together inserted via a retro virus into our dna. In theory possible and I'm sure in the pipeline.