What has been happening to duodenal ulcer?
D000328:Adult; D000349:Africa; D000368:Aged; D004381:Duodenal Ulcer / Q000453:epidemiology* / Q000209:etiology / Q000266:history; D004739:England; D005260:Female; D049673:History, 20th Century; D006801:Humans; D008297:Male; D008875:Middle Aged; D012606:Scotland; D013276:Stomach Ulcer / Q000453:epidemiology; D014481:United States