title: The origins of vaccinia virus.
mesh_terms: D000818:Animals; D002417:Cattle; D049671:History, 18th Century; D049672:History, 19th Century; D049673:History, 20th Century; D006736:Horses; D006801:Humans; D006824:Hybridization, Genetic; D008829:Microbiology / Q000266:history*; D014611:Vaccination / Q000266:history; D014615:Vaccinia / Q000209:etiology / Q000266:history; D014616:Vaccinia virus; D012901:Variola virus