YELLOW FEVER 127 



When an outbreak does occur measures for the 

 destruction of the larvae must be most energetically 

 pushed. 



For the success that has attended such prophylactic 

 measures the reader is referred to the reports as to 

 the sanitation of Havana, New Orleans, and the Panama 

 Canal Works. 



Importation of disease is usually by ship. Either 

 infected mosquitoes are introduced or infected persons. 

 Infected mosquitoes may be brought in with the cargo 

 or in private baggage, and in that case the focus of the 

 epidemic is the place where the baggage is opened. 



Ship Epidemics. S. fasciata can thrive on board 

 ship, and can be transported for long distances by sea 

 as eggs, larvae, or adults. The adult mosquitoes may 

 be infected in one port, and only become infective 

 after reaching a second port, and then may give rise to 

 an epidemic in the vicinity of the wharves. It is quite 

 possible in a voyage of a week or less that the crew of 

 the ship might escape infection, and the source of infec- 

 tion of the port would not then be known. It is different 

 in cases where the mosquitoes become infective whilst 

 at sea. In such a case a large proportion of the sus- 

 ceptible crew may acquire yellow fever. 



The mosquitoes need not be numerous, but every 

 attempt must be made by fumigation of one part of 

 the ship after the other to destroy any mosquitoes, and 

 the sweepings, as on land, must be burnt at once. 

 S. fasciata become torpid with cold, and consequently 

 such epidemics subside four or five days after reach- 

 ing colder latitudes, but in summer may continue active 

 and develop as far north as England, and may spread 

 in the vicinity of the wharves as the mosquitoes escape 

 from the ship. In some cases the infection has remained 

 in the ship for several months, even when it has not 

 been occupied for this period. In a sheltered warm 

 part of a ship these mosquitoes may live for that period. 



The history of yellow fever deserves special notice, as so 



