title: A historical account of the rickettsial diseases with a discussion of unsolved problems.
mesh_terms: D049671:History, 18th Century; D049672:History, 19th Century; D049673:History, 20th Century; D011778:Q Fever; D012282:Rickettsia Infections / Q000453:epidemiology / Q000266:history* / Q000517:prevention & control / Q000628:therapy; D012373:Rocky Mountain Spotted Fever; D014437:Typhus, Endemic Flea-Borne; D014438:Typhus, Epidemic Louse-Borne; D014481:United States