138 MODE OF TRANSMISSION OF YELLOW FEVER 



VI list ellipse before the mosquito is itself i/feetive, and 

 eapable of transinittiiig tlie virus ; approccimatelij this 

 period is twelve dai/s. 



Therefore, at the termination of the period of 

 incubation in the mosquito, fresh cases of infection 

 may be expected to occur in those living in a house 

 in which the mosquitos were not destroyed. 



The symptoms of disease will also not declare 

 themselves in man at once, for, as just seen in the 

 case of the mosquito, an incubation period is also 

 necessary in the case of man, and the period is usually 

 five days. Consequently an interval of a little over 

 two weeks usually occurs before secondary cases 

 manifest themselves. 



SUMMARY 



1. Man suffering from yellow fever after the fifth 

 day is the reservoir. 



2. From this reservoir one species of mosquito, 

 the Stegomyia ealopiis, becomes infected and after the 

 twelfth day becomes the insect earrier or transmitting 

 agent of the disease. 



3. The reservoirs and the carriers are both necessary 

 for the spread of the disease. 



4. Method of attack. 



{a) Prevent entry of reservoirs (quarantine 

 measures, etc.). 



{b) Exterminate the carrier (anti-adult mos- 

 quito measures, screening, fumigation, 

 etc., anti -larval measures, control of 

 water supply, oiling, drainage). 



