Vaccinia epidemic and epizootic in El Salvador.
D000818:Animals; D002417:Cattle; D004544:El Salvador; D006385:Hemagglutination Inhibition Tests; D006801:Humans; D009500:Neutralization Tests; D012423:Rural Health; D014611:Vaccination / Q000009:adverse effects; D014615:Vaccinia / Q000453:epidemiology* / Q000209:etiology / Q000662:veterinary*; D014616:Vaccinia virus / Q000302:isolation & purification