The source of vampirism is the Human Vampiric Virus (HVV). Like Rabies, HVV belongs to the order Mononegavirales, viruses with a nonsegmented, negative-stranded RNA genome. Viruses in this group have a distinct bullet shape. The virus' natural host is a flea commonly found on cave-dwelling bats, especially the vampire bat. In the most common scenario, a bat which has been bitten by the flea passes the virus on to livestock and humans through a bite.