title: West Nile virus heads west.
mesh_terms: D000818:Animals; D001715:Bird Diseases / Q000453:epidemiology*; D001717:Birds; D002170:Canada / Q000453:epidemiology; D006801:Humans; D014481:United States / Q000453:epidemiology; D014901:West Nile Fever / Q000453:epidemiology* / Q000401:mortality / Q000662:veterinary*