((This post is about quarantining. If you want to just skip to the story, the next story post is "Winter 266, Nutscaves"))
Everything in a safe DF2010 fortress revolves around the dwarven bathtubs. Dwarves must be funneled through a smoothed and engraved dwarven bathtub whenever they enter or leave the hospital, the soil layers of the fortress, or any cavern. These bathtubs are incredibly dangerous, in a way, because they gather contaminants off of dwarves and objects (which then emerge clean with a coating of water).
Coming in contact with contaminants is what causes plague. The engravings in the tubs help ensure the tubs get prioritized for cleaning regularly. I find they are usually cleaned within a week of contamination even with forty dedicated, stationed janitors standing in the tub. In sum, tubs alone will never save you.
The tubs do not prevent the plague. They just prevent infected substances from escaping the caverns and Nutscaves' contaminated soil (upper) levels. The contaminants cannot get into the rock layers where most dwarves live and work unless they are already there, or a bathtub fails by becoming dry. (Such as that incident when the well went dry*, and everyone decided to give patients water from the hospital bathtub until it dried up.) ((* That incident was told orally.))
Bathtubs do not get dry on their own once they have depth 2/7 or more water in them. This depth prevents evaporation. It's dwarven physics.
When a dwarf gets wet in the bathtub, his Water Coating seems to temporarily prevent him from getting contaminated further. I keep all dwarven forays into the caverns, which are full of forgotten beast poison, as brief as possible. This ensures the dwarves keep their protective water coating. When I chop cavern wood, I select very small areas and stop the wood cutters if it's starting to take too long. I don't let my wood cutters haul wood--the wood haulers can zip in and out and keep a water coating to do that bit safely, while I keep my eye on the woodcutters and minimize their time spent working. The less total time the dwarves spend in the cavern chopping, the less micromanagement I have to do.
When we haul a forgotten beast corpse from the spike traps in the caverns to the butcher, the hauler also gets the water coating. So far I haven't had any of them get contaminated with extracts or deadly blood. (Part of the reason I continue to keep my caverns open instead of permanently sealing them, is because I continue to test whether this water coating really works as contaminant prevention. So far it seems to.)