trying to get a dracula book title

Hi,

I read a book about 10-15 years ago that I remeber liking it and I
would like to read it again but I cant remember the title. The
storyline is something like follows: it is set in current time and the
historical time of vlad tepez in Rumania and the US. I remember
something about some orphanage in Romania, transylvania, and the idea
of a rare genetic blood disorder that in fact was the driving force of
"vampires".

Any ideas?

Thanks,

Fredric