16 INSECTS AND HUMAN WELFARE 



There is no yellow fever, except an occasional stray case from 

 the tropics, which does not get beyond the keen eyes of the 

 Public Health Service, and consequently our population of 

 yellow-fever mosquitoes remain free from the dread disease. 

 In this case several factors have combined to make possible 

 the elimination of the disease without more than temporary 

 and local eradication of the mosquito. In our southern states 

 the disease does not easily survive the winter and chronic 

 human carriers do not exist, so that past outbreaks have been 

 due to fresh introductions and have been terminated by cold 

 weather. During the last epidemic that occurred in New 

 Orleans, in 1905, vigorous anti-mosquito measures were 

 necessary, but, due to the greater severity of the disease, the 

 consequently greater ease with which it is recognized, the 

 limited area to be dealt with, and the absence of chronic hu- 

 man carriers, the eradication of yellow fever without perma- 

 nent mosquito repression has been easy in comparison with 

 the control of malaria. The success of this campaign has 

 undoubtedly sounded the death knell of the yellow-fever 

 epidemic and panic in the United States, for New Orleans 

 has amply demonstrated what may be accomplished in the 

 control of an epidemic by an efficient group of workers, 

 backed by a sympathetic public and supplied with reasonable 

 funds. Even in parts of the tropics where it persists through- 

 out the year, it is being rapidly and permanently eliminated. 

 Indeed it bids fair to be the first disease actually to become 

 extinct as a direct result of human discovery and applied 

 science. What a refreshing contrast to the fate of the Ameri- 

 can pigeon and the forlorn remnants of the American bison ! 

 Another tropicopolitan, semi-domesticated mosquito ex- 

 tends quite widely into the warmer parts of the United States 

 (Fig. 6). This is Culex fatigans, now known as Culex quinqve- 

 fasciatus (Fig. 7), responsible for the transmission of dengue 

 fever or "break-bone fever." Dengue is a mild (i.e., non- 

 fatal) disease which causes great distress and temporary 

 disability. It is therefore a factor contributing to lack of 

 efficiency and goes hand in hand with malaria in this respect. 



