13 



Section C 



Obviously there are two methods by which vessels can become 

 infected, (a) A case of yellow fever contracted elsewhere may develop 

 aboard a vessel already harboring stegomyia mosquitoes which become 

 contaminated from it. (6) The stegomyia mosquitoes may come aboard 

 already contaminated. In the first case, there being nearly always over 

 two weeks between the infecting and the first secondary cases of yellow 

 fever, it results that, if the first case occurs after leaving port, vessels, 

 even sailing vessels, from Cuba and the Caribbean Sea will generally 

 reach quarantine and (if at a southern station) be disinfected — i. e., 

 mosquitoes killed, before it is time for the secondar; cases to develop, 

 or, indeed, to be contracted. This agrees with all observation. In 

 vessels infected in the second way, cases of yellow fever may occur 

 after a very short or no interval from leaving port. The causes, then, 

 which have lessened the number of infected vessels at United States 

 ports, are — 



1. The very great falling off of vessels from Eio de Janeiro and 

 Santos since the establishment of the Brazilian Republic. This does 

 away with the bulk of the "long- trip vessels" we used to have, which 

 are the only ones developing secondary cases en route if infected by a 

 case of yellow fever developing aboard. (Vide a.) 



2. The replacing of sailing craft by steamships. That steamers con- 

 vey yellow fever less frequently than sailing vessels has long been known. 

 This is because they lie a much less time in an infected port, and the 

 discipline of their crews is better ; no shore leave means no man goes 

 ashore. They also make quicker trips, and thus are not apt to develop 

 secondary cases en route, even if yellow fever contracted elsewhere 

 develops aboard and they have the stegomyia aboard. It is also to be 

 noted that the worst parts of the harbors of Havana and Eio de Janeiro, 

 above San Jose wharf and the Gamboa, have never been berths for 

 steamships. Note, too, that the sailing vessels displaced are the foreign 

 sailing vessels; the American schooner was less often infected than 

 foreign vessels. 



3. Especially since 1893, and to some extent before supervision had 

 been kept by United States sanitary inspectors in the more dangerous 

 yellow-fever ports over vessels bound for the United States, especially 

 of passenger vessels. Certain anchorages have been recemmended as 

 safe, others have been forbidden, notably the Gamboa at Rio de Janeiro 

 and certain wharves and parts of the harbor at Havana. Passengers 

 who it is believed will develop infection aboard have been barred ; ship- 

 ment of new men in the infected port carefully supervised ; vessels in 

 which yellow fever has occurred in port are disinfected before leaving, 

 and many other measures taken to have the vessel leave port clean, or 

 as nearly clean as commercial considerations allow. In general, the 

 vessel owners, especially of the regular lines, have given hearty coopera- 

 tion in these measures, as well as in keeping the crew aboard and in 

 confining the visits of such officers as must go ashore to daylight. 



3 SEC. c. 



