Right, so I'd finally gotten a huge orchard set up. All kinds of fruits and stuff, all planted and tended so that the harvests were staggered all year. Then I downloaded the latest update, and updated my save game for it.
A few months into playing, and a few of my apple trees are dying. Shit, well, that's okay. I loo'k' at them, and it says, "Diseased". Hmm. Wierd. Must be the new update. Anyway, I keep playing, and figure that the rest of the apple trees will die, but I've got a ton of different fruit trees.
Another few months pass, and all the apple trees are dead. I sigh, and write it off. Another month passes, and an orange tree is dying. Well, shit.
Then I read the update.
"...also I added some randomly generated diseases, some of which can get pretty nasty. Some of them continue to randomly generate to simulate evolution, and some just stay the same and are treatable. It's pretty neat, but during testing, I got an outbreak of what I call, "Spinal Flu" that left my whole fortress parapalegic, then started killed all my livestock..."
Shit. Well, at least it's just the fruit trees. A year passes, and my whole orchard is dead. My orchard tenders have gone insane from watching their trees die.
And then I see something horrifying. The lead treetender has 'Diseased'. I check his description. Dear god, it's eating his skin and bones, but nothing else.
And it spreads like wildfire. But the tantrum spiral spreads faster. As dorfs start dying, people start flipping out, breaking things, rioting, looting, murdering each other. Finally, all I have left is the mayor and several of his bodyguards, locked hermetically on the other side of a several squares thick granite wall, and a couple plague victims slowly dying.
The final plague victim, before he dies, crawls into the air vent network right outside the Mayor's safe room, and starts breaking the air filters...
Your fortress has crumbled to its end.