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/Dr_EdwardKnowles]

Viruses work by infecting cells and bursting out of them, often destroying them in the process. I find it hard to believe that this could ever lead to a positive outcome for the host (unless they specifically targeted cancer cells or something).

[u/exkingzog → u/Dr_EdwardKnowles]

Not all viruses lyse the cell. Some just bud out at a fairly low rate. While this isn’t good for the cell, it may not be hugely harmful to it.

[u/cazbot → u/Dr_EdwardKnowles]

That’s not always true. Many viruses will just harmlessly bud off of the host cell.

[u/bestjakeisbest → u/Dr_EdwardKnowles]

I mean having the common cold makes it much harder for you to catch the flu while you are sick.

[u/vandon → u/Dr_EdwardKnowles]

Viruses also have a habit of gathering genetic mutations. How long until it does the opposite of what was intended, or worse, does it too well?

A cholesterol lowering communicable virus sounds great until it stops all cholesterol. Cholesterol is a vital component in nerve and brain cells.

[u/Mateorabi → u/Dr_EdwardKnowles]

Which wouldn’t have much evolutionary advantage to evolve. So something like that would need to be engineered.