title: Derivation of an isolate of low virulence from the Essex '70 strain of Newcastle disease virus.
mesh_terms: D000336:Aerosols; D000818:Animals; D002642:Chick Embryo; D002645:Chickens; D004531:Eggs; D004739:England; D006386:Hemagglutination Tests; D009522:Newcastle disease virus / Q000276:immunology / Q000472:pathogenicity*; D011201:Poultry Diseases / Q000209:etiology; D012140:Respiratory Tract Diseases / Q000209:etiology / Q000662:veterinary; D014613:Vaccines, Attenuated; D014765:Viral Vaccines / Q000008:administration & dosage; D014774:Virulence
chemical_list: D000336:Aerosols; D014613:Vaccines, Attenuated; D014765:Viral Vaccines