title: Weekly update: West Nile virus activity--United States, September 19-25, 2001.
mesh_terms: D000818:Animals; D001715:Bird Diseases / Q000453:epidemiology*; D001717:Birds; D009033:Culicidae / Q000821:virology*; D006734:Horse Diseases / Q000453:epidemiology*; D006736:Horses; D006801:Humans; D014481:United States / Q000453:epidemiology; D014901:West Nile Fever / Q000453:epidemiology* / Q000662:veterinary*; D014902:West Nile virus / Q000302:isolation & purification*