Egon Spengler: Notice the vacant stare, the completely mindless look. That could only mean one thing.
Winston Zeddemore (I): She's from California?
Egon Spengler: No. She's been hypnotized.
Ray says that it's the very first time they've dealt with vampires. In Season 2 Episode 25, "No One Comes To Lupusville", the Ghostbusters had to deal with both werewolves and vampires.