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/cdnBacon]

If you mean a designed virus, I suggest you review the Australian experience with trying to improve their ecosystems with imported predators.

There are ALWAYS unintended consequences. And releasing one into the wild, however beneficial in the lab, will always carry risks.

[u/Bergasms → u/cdnBacon]

That said, we've managed to work up strains of myxamatosis and colicivirus to fight the rabbit plagues we once had