YELLOW FEVER 125 



crowded business quarters of a town, usually near wharves 

 and the shipping. The possibility of the disease being 

 carried in an attenuated form through several generations 

 of mosquitoes cannot be excluded. 



Till a parasite which can be detected at all stages of the 

 disease or in infected mosquitoes has been discovered, 

 the subject is a fruitful one for the proposal of hypotheses, 

 but the method of prophylaxis to the extent of eradicating 

 the disease is more difficult. Whatever hypothesis may 

 be adopted as regards the reservoir, natives, rats or other 

 animals, there is no doubt that S. fasciata is the carrier 

 and the success in Cuba and Panama of measures based 

 on the destruction of this mosquito have -been strikingly 

 successful, whether or not this will convert a partially 

 immune resident population into a highly susceptible 

 population depends on whether the disease is carried on 

 in the reservoirs in an attenuated form or is reintroduced. 



We are not yet in a position to relax any quarantine 

 regulations. The introduction in the past of cases of 

 yellow fever in a virulent form has been followed by 

 outbreaks of the virulent form of the disease ; and by 

 quarantine alone, even without the isolation of cases, many 

 of the West Indian Islands and British Guiana were free 

 from virulent cases for from ten to twenty years without 

 any reduction in the number of Stegomyia. 



In case of an outbreak, protection from mosquitoes, both 

 day and night, of all infected cases, protection at night of 

 all susceptible persons, destruction by fumigation of all 

 house mosquitoes, and of the larvae and breeding-places 

 of S. fasciata, would render the outbreak easily con- 

 trollable. 



There is no risk of spread of yellow fever in a town 

 where S. fasciata has been exterminated, nor in a house 

 where there are no breeding-places for this mosquito 

 near. 



In a town not so protected, or only partially protected 

 so that some mosquitoes of the species S. fasciata are 

 present, the introduction of a patient with yellow fever 



