576 Yellow Fever 



became able to impart yellow fever through their bites. This in- 

 fectious character, having once developed, seemed to remain through- 

 out the subsequent life of the insect. So far as it was possible to 

 determine, only one species of mosquito, Stegomyia calopus, served 

 as a host for the parasite whose cycles of development in the mos- 

 quito and in man must explain the symptomatology of yellow fever. 



In order to establish these observations, experimental inocula- 

 tions were made upon human beings in sufficient number to prove 

 their accuracy. Unfortunately, Dr. Lazear lost his life from an 

 attack of yellow fever. 



Reed, Carroll, and Agramonte* came to the following conclusions: 



1. The mosquito C. fasciatus [Stegomyia calopus] serves as the intermediate 

 host of the yellow fever parasite. 



2. Yellow fever is transmitted to the non-immune individual by means of the 

 bite of the mosquito that has previously fed on the blood of those sick with the 

 disease. 



3. An interval of about twelve days or more after contarnination appears to be 

 necessary before the mosquito is capable of conveying the infection. 



4. The bite of the mosquito at an earlier period after contamination does not 

 appear to confer any immunity against a subsequent attack. 



5. Yellow fever can be experimentally produced by the subcutaneous injection 

 of blood taken from the general circulation during the first and second days of the 

 disease. 



6. An attack of yellow fever produced by the bite of a mosquito confers im- 

 munity against the subsequent injection of the blood of an individual suffering 

 from the non-experimental form of the disease. 



7. The period of incubation in 13 cases of experimental yellow fever has varied 

 from forty-one hours to five days and seventeen hours. 



8. Yellow fever is not conveyed by fomites, and hence disinfection of articles 

 of clothing, bedding, or merchandise, supposedly contaminated by contact with 

 those sick with the disease, is unnecessary. 



9. A house may be said to be infected with yellow fever only when there are 

 present within its walls contaminated mosquitoes capable of conveying the para- 

 site of this disease. 



10. The spread of yellow fever can be most effectually controlled by measures 

 directed to the destruction of mosquitoes and the protection of the sick against 

 the bites of these insects. 



11. While the mode of propagation of yellow fever has now been definitely 

 determined, the specific cause of the disease remains to be discovered. 



The probabihty that Bacillus icteroides is the specific cause 

 and is transmitted by the mosquito is so sUght that it need scarcely 

 be considered. All analogy points to the organism being an animal 

 parasite similar to that of malarial fever. 



With this positive information before us, the prophylaxis of 

 yellow fever and the prevention of epidemics of the disease where 

 sporadic cases occur becomes very simple and may be expressed in 

 the following rules: 



1. Whenever yellow fever is likely to occur, the breeding place of mosquitoes 

 should be destroyed by drainage. Cisterns and other necessary collections of 

 standing water should be covered or secured. 



2. Houses should have the windows and dpois screened and the inhabitants 

 should use bed nets. 



* Pan-American Medical Congress, Havana, Cuba, Feb. 4-7, 1901; Sanitary 

 Department, Cuba, series 3, 1902. 



