186 OTHER SPOROZOA 



of tropical cities which have been cleared of the disease which once 

 made them highly dangerous to visitors and a menace to the 

 rest of the world. In connection with an incessant war on the 

 transmitting mosquito in all stages of its life history, all known 

 or suspected cases of yellow fever should be carefully screened 

 so that mosquitoes can have no access to them. Personal pre- 

 vention in endemic regions consists in avoiding mosquito-haunted 

 places at all times when Aedes calopus is likely to be active. 



Dengue 



Dengue, seven-days' fever, or breakbone fever, is a disease of 

 tropical and subtropical countries. It is very common in the 

 West Indies and great epidemics have swept through Panama, 

 the eastern Mediterranean and southern Asian countries, the 

 Phihppine Islands and various South Sea Islands. An epidemic 

 has recently been reported from Argentina and Uruguay, the dis- 

 ease supposedly having been introduced from Spain. Dengue also 

 occurs in southern United States where it is probably often over- 

 looked, being diagnosed as something else. In some places, e.g., 

 southeastern Europe and India, there is some confusion between 

 dengue and phlebotomus fever. Both diseases vary somewhat 

 and mild types of the former and severe types of the latter may 

 easily be, and frequently are, confused. Dengue occurs in the 

 form of sudden and rapidly spreading epidemics which sweep 

 over limited areas, affecting a large per cent of the popu- 

 lation. 



Nearly every fluid and organ of the body has been examined 

 in an effort to find the organism causing dengue,- but although 

 many supposed parasites have been found, the true cause of the 

 disease is still unknown. In at least one stage of its life history 

 the parasite, like that of yellow fever, is ultra-microscopic. That 

 the disease is transmitted by the tropical house mosquito, Culex 

 quinquefasdatus, and, in Australia at least, by Aedes calopus, has 

 been proven by experimentation. The distribution of dengue 

 coincides almost exactly with the geographic range of Culex 

 quinquefasdatus. 



Unlike yellow fever, dengue has a very short incubation period 

 in the mosquito — in one experiment it was only 48 hours. 

 This fact, together with the short incubation period in the 



