The Testing Point
Hostage to a marriage he never would have chosen, Devryn nonetheless finds his new husband, Rowe of Relganor, at the very least tolerable, though his father the King is a tyrant who holds his domain in thrall. But then the scalding sweat strikes the kingdom, and at the testing point, it seems both have more courage - and more in common - than they might have guessed.
From fail-fandomanon.dreamwidth.org: "A marriage of state between a king's younger son and a conquered land's son. When the prince falls ill of a plague, his consort uses his medical knowledge to nurse him back to health."
The Testing Point has no connections to other stories or universes.
Also available on Archive of Our Own under the pseud Atalan.
I've had this scenario in my head for a very long time... one half of an arranged marriage, whose life would probably be improved by the death of their partner, nonetheless taking a considerable risk to save their life because the idea that everyone else would walk away is just too appalling.
The Scalding Sweat is not a real disease but I did spend some time working out the mechanics of it. It's spread from one infected person to another by bedbugs, which is why it sometimes gets everyone (in places where sharing beds is common, and if infected travellers stay at inns) and sometimes doesn't spread at all.
I'm working on a longer, novel-length version of this story. Although I like how it came out originally, I felt I had to cram a lot of stuff in quickly to get the world up and running, and the ending was too abrupt. The novel version will have a more gradual relatonship build-up, and a follow-through on the rebellion against the King.