Dracula arrives in England just as a new disease might arrive, on a boat. He summons hoards of rats, and his infective evil spreads from the first woman he bites to the children she feeds on, unwittingly, at night. What makes Dracula particularly terrifying, and what takes the plot of the story so long to resolve, is that he is a monster whose monstrosity is contagious. Germ theory was widely accepted by 1897, when Dracula was published, but only after having been ridiculed earlier in the century.
