 Strong Wamphyri maintain their psychic powers to some degree after death, and if enough of the vampire's body remain in the soil, the vampire can eventually be reborn in the fungus stage, with consciousness intact.Vampirism is highly infectious, and even small touches can eventually cause conversion.In the case of Lady Karen, if denied sustenance long enough, the Leech may make a desperate bid for survival and flee the human host, leaving them in a mostly human state (presumably, if the leech fled a host in a transformed or mutated form, the host would stay in that form).