Actually, Soma DOES know about the historic Dracula.
When you have the dialogue with Genya Arikado at the beginning of Aria of Sorrow, Soma actually acknowledges this:
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Arikado: Why have you come here?
Soma : Why? Well, Mina and I...hang on, where are we?
Arikado: We're in Dracula's castle.
Soma : Huh? Dracula's Castle? Are you telling me we are in Europe?
Arikado: No, we are inside the solar eclipse.
Soma : Inside the eclipse?! Are you insane?! Do you think I'm a fool?!
Mina : Soma! Listen to him, he's telling you the truth!
Soma : What the heck are you talking about? Give me an explanation!
Arikado: Well, it's like this...huh?! An enemy!
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So, clearly Soma knows about Dracula's Castle, so he knows the historical figure "Dracula". He may or may not know Bram Stoker's version of "Dracula", but he certainly knows that Dracula is some kind of figure from Europe.
If Soma does not at all know that Dracula declared a War on Humanity and there was a huge conflict in 1999 in Europe, then this is most likely covered up by the parties involved. Sort of a "Men in Black" scenario (and Genya fits this role to a T, plus with the ability to Glamour people since he's a Dhampir...).
It's likely that the Church and a few governments and organizations did their best to cover up anything regarding this event, to prevent it from causing a panic in the regular world... so most people would just not know about it. Back in 1999 the Internet was still somewhat in its infancy and there were no big things like Youtube and Cellphone Videos, etc. so it's somewhat more plausable that an event of such magnitude can be covered up.
If someone did spot anything, it would just be some kind of weird sighting.
Something that may cause some kind of watchgroup, such as
ASFAN or something.
I'm not an ASFAN. I'm more of a BOOBFAN. Ha ha! I'm here all night, folks.