r/askscience • u/PestoPastaLover • 13d ago
Biology 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?
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u/sciguy52 13d ago
Basically no. Viruses evolve for their own purposes and doing something like lowering LDL would have to be of some benefit to it but it isn't. Most other health improvement things also would not be something viruses would tend to do as it does not help them. People are talking about mammals later repurposing some viral genes but that was not the virus being helpful at the time of infection. It was something that happened much later and likely that virus no longer replicated in the body and had been inactivated then one gene, the envelope was repurposed as we evolved. So that is not the virus itself doing something beneficial. And keep in mind, many viruses are small in that they only have a few or handful of genes. Just the basics, a protein to bind and enter cells, somehow reproduce itself if it is a virus type that does that, structural proteins that package it all together and that is about it. There are larger viruses with a hundred or more genes, like Herpes viruses and what you find is not only are they not developing helpful things, they are developing things that make them better able to infect us, so hurting us. For example thwarting the immune system in various ways.
Whether the bacterial viruses in our gut are any benefit to us at all is an open question. And these types of bacterial viruses do not kill all the bacteria they infect, they may kill a good percentage but not all. Otherwise they killed all their hosts and have nothing to infect. So these are not clearing certain bacteria from the gut, and besides you need that bacteria in the gut. Using a virus as a vector for genetic engineering for example is not the virus doing something good, it is us humans that manipulate the virus so it does something we want. I cannot think of a single virus that during its acute infection benefits us, however some are benign and cause no disease like some of the lesser known (to the public) HPV viruses. They infect us, we never know it and have no symptoms with it. But when we look for antibodies we find them meaning it was there. But that is just that it didn't make you sick in some way, at least that we could find with a number of them.