The epidemiology and clinical features of smallpox.
D000293:Adolescent; D000349:Africa; D001208:Asia; D002648:Child; D004196:Disease Outbreaks; D005260:Female; D006801:Humans; D008297:Male; D012899:Smallpox / Q000175:diagnosis / Q000453:epidemiology* / Q000517:prevention & control; D006113:United Kingdom