system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: why is it so hard to make a virus killing drug?
gpt
Viruses aren't alive in the "drug can kill them" sense. They're just complicated balls of proteins and DNA floating around. You can't kill what isn't alive, the only thing you can do is destroy it. Unfortunately, any chemical that destroys random proteins and DNA will also kill...you. 

So the only thing you can do is design a \*very\* specific molecule that is exactly matched to the virus proteins and nothing else. Which is exactly what your immune system does, but it takes time and it's very very specific to one particular virus...it won't work on anything that doesn't have matching proteins. 

Basically, every virus would need it's own drug and that drug would be stupid complicated...manufacturing protein drugs is very difficult, they're really big complicated molecules. It's \*far\* easier to keep you alive while your immune system figures it out, or train your immune system in advance (this is what vaccines do).