Page:Tropical Diseases.djvu/290



Definition.— An acute, specific, very fatal febrile disease occurring epidemically, or as an endemic, within a peculiarly limited geographical area. Though subject to great variations, its typical clinical manifestation may be said to be characterized by a definite course consisting of an initial stage of a sthenic nature, rapidly followed by an adynamic condition in which such evidences of blood destruction as black vomit, albuminuria, and hæmatogenous jaundice are liable to occur. One attack generally confers permanent immunity. The germ is transmitted by the domestic mosquito, Stegomyia calopus (S. fasciata). Geographical distribution.— Of all the important zymotic diseases, yellow fever has the most restricted geographical range. Its centre is the West Indies, whence it spreads north to the United States and Mexico; south to the Brazils and, at times, as far as Buenos Ayres and Monte Video; west to Central America, and across the Isthmus of Panama to the Pacific coast, along which it extends north to the Gulf of California and south to Peru. It occurs also, in epidemic form, on the West Coast of Africa, where it appears to be endemic. It is impossible to determine from existing records whether yellow fever was originally an African or a West Indian disease. Yellow fever has been imported frequently into Portugal and Spain, and once from Spain into Italy. Although a good many died in these visitations, the disease has never obtained a permanent footing in Europe. Cases have occurred in seaport towns in France and Great Britain - Brest and Swansea, for example; invariably, however, these little epidemics have died out.

In several of the West India Islands yellow fever is