XI] GEOGRAPHICAL DISTRIBUTION 183 



On the West Coast of America the general conditions are so 

 unfavourable to the breeding of the mosquito, that the disease 

 has not been able to establish itself and has only appeared 

 sporadically in one or two localities, with the exception of 

 the Isthmus of Panama, which until recently was one of the 

 noted endemic centres. With this exception, therefore, the 

 West Coast has never been the scene of any severe epidemics, for 

 comparatively few ships sail up the coast and consequently there 

 has been little chance of their spreading infected mosquitoes. 

 Colon is practically the only port that has hitherto been liable 

 to infection, but with the opening of the Panama Canal and 

 the increase in trade which this is sure to effect, the question 

 of the possibility of thus extending the range of yellow fever 

 will have to be carefully considered. The recent outbreak at 

 St Nazaire in 1908 has shewn clearly that even modern ships 

 are capable of carrying infected Stegomyia for considerable 

 distances. 



In Europe the appearances of the disease have been 

 very similar to those in North America, and many epidemics 

 occurred during the eighteenth and nineteenth centuries, 

 when the growth of commercial intercourse resulted in an 

 increase in the number of ships coming from endemic centres. 



In Southern Europe numerous epidemics of considerable 

 severity have occurred, and the ports of France, and even 

 Swansea and Southampton in England, have been the scenes 

 of small outbreaks. In the south of Europe Stegomyia fasciata 

 is capable of breeding, and therefore epidemics could easily 

 become established during the summer months, but in the 

 more northerly regions this is out of the question. In these 

 cases the infection is strictly limited to persons who have 

 been near a ship carrying infected mosquitoes on board. 



Thus in the case of the outbreak at St Nazaire in 1908, 

 infected Stegomyia were taken on board a ship at Martinique. 

 These were carried across the Atlantic and on arrival at 

 St Nazaire, several of the mosquitoes escaped and fed on 

 persons either on board or in the vicinity of the ship. Eleven 

 individuals were known to be infected in this way, of whom 

 seven died. 



