Having a nice colony is great and all, and sure the raiders are pretty horrible sometimes, but doesn't it just feel like something is missing? Bodies smell bad and colonists don't like that, but it doesn't infect them. Raw food is eaten and nothing. Squirrels carrying diseases go insane and bite people but they're fine apart from scratches.
It'd be nice to have viruses able to contaminate colonists, with different types per occasion and separate methods of spreading -- contact, airborne, bloodborne, or special cases for some.
Of course, it'd need to be able to be stopped. The doctoring role could take precedence in delivering colonists into a new bed type, quarantine. Anyone marked for infection would be taken and locked up like a prisoner -- but that just stops spread, it doesn't cure the disease. Late-game there should be a set of workplaces like an isolator to separate the virus from the infected's blood (allowing doctors to remove blood from patients) and a centrifuge to create antibodies from the virus. Anyone injected with the antibodies will be cured from the virus and unable to be infected by the same one permanently.
I like this idea solely for the idea that I could fling raider bodies at enemy siegers.
But yeah, some sort of sickness or disease caused by bodies would be a nice incentive to keep people out and keep your base clean.
The Doctor job isn't implemented yet. Give it time.