Vampires can be a great boon to your fortress, or the end of it. Either way it's always a good idea to make sure you know about all the vampires in your fort. Sometimes death is necessary to insure the continual growth of the fortress, however vampires can also be the saviors of your fort.
Safe:
-Your starting 7 are always clean, it's migrants you need to watch out for.
-Carvans also appear clear so far.
-Children born in your fort are clean as well, and possibly even those born to vampire parents won't have vampirism.(confirm?)
Detection:
-Always check your migrant's bio. If you see a long list of "form member of ...." this is so far the most common warning of a vampire.
-Another red flag is a young age for an otherwise experienced dwarf.
-Check their relations they have, so far a 100% way to tell if your dwarf is a vampire is by giving them a standout profession nickname, then view the history of their diety. Once you find your dwarfs name read the description. This should state that "Diety has recieved worship for dwarf vampire "their name" or "Diety has cursed dwarf vampire "their name" to prowl the night in search of blood...".
-Another relationship check is by looking at their relatives if this is possible. If the younger sister is somehow older than your suspect things might not be as they seem.
-Also your dwarves can't be expected to pick up on this, they'd confuse their own mother as urist mcvampire.
-Dieties will also curse dwarves with vampirism, so if your suspect worships a diety that has done this in the past and you don't want to go through all the history consider this another bit of evidence.
Confirming:
-Best way is to seal them off in their own little area. If they get hungry or thristy they are probably not a vampire. However vampire dwarves do still carry on their love of beer, and will work slower if cut off from the stuff. (I'm guessing this is because of the BAC of dwarf blood.)
-Another way is to select them for a burrow with a brave soul(victim). Leave them be for about a month in the area. If urist mcvictim goes missing, you know who it is.
-To get dwarves to notice this use structures that allow vision in a busy hall. Vampires don't seem to notice that fortifications allow others to notice their activities. All you need to do is arrange the meeting.
-Give the suspected vampire a nickname or noble title, if the nickname does not appear it is because they are using a fake name.
-Appears vampires don't suffocate, use this knowledge wisely.
Anyone who has any more information to add would be great, or correct me if I made a mistake. I would go on as to what to do but their are many ways to have fun with this, so i'll let you decide what to do with your vampires.