I was trading with my fellow dwarves. I only have them as trading partners; I thought I'd get elves as well, since I embarked on the main continent of a small map (I refuse to play on a map larger than that until the outcasts stop piling. I learnt my laggy lesson). Apparently I embarked too far, and into a savage saltwater marsh.
Humans, there are only two of them left in the world, both male, each at opposite sides of the world. They are doomed to go extinct. Good riddance. Filthy, savage, useless tallfolk!
Anyhow, as I was discussing useless crap with the outpost liason, who is an elven woman by the way, a weretapir invited itself over to my fort. Merchant guards engaged it with crossbows. The weretapir launched itself over to some poor gem cutter guy who was hauling wood at the moment, whizzing past the guards who kept shooting at it.
It killed its first target quick, and started to fight with the guards who had apparently emptied their quivers and were charging onto it. Some of my dwarves also joined into the carnage, and together they overwhelmed the beast, with the final blow pushing it inside a murky pool, where the corpse rot away.
I immidiately paused the game to see if any my citizens got infected. It turns out two dwarves had contracted the curse. I knew they would transform and spread the weretapir curse, and that things would go out of control eventually.
I assigned them both to a militiary squad, sent them down to a mining tunnel and sealed it shut behind them, along with some cats which entered in while the wall was being built. I then disbanded the squad. They are trapped there forever now.
They are there to this day. Each month, I get two reoccuring notifications. The cats are still there too, weretapirs do not kill them for some reason, and it turns out one of them was pregnant. A healthy population of cats is sure to develop there in time.