YELLOW FEVER PROPHYLAXIS IN NEW ORLEANS 13 



great variations of temperature, the cold increasing as I travelled 

 from New Orleans to New York and from New York across the 

 Atlantic to Liverpool. The journey occupied 25 days, and they 

 were only supplied with clean water. The larval is succeeded 

 by the pupa stage which lasts two days or under, and from the pupa 

 arises the imago, or winged mosquito. 



In comparison with the Culex and Anopheles, Stegomyia larvae 

 develop very quickly, and this is well seen if bottles containing 

 mixtures of Culex and Stegomyia larvae are put to develop, the latter 

 will hatch out much more rapidly than the former. 



The Infected Stegomyia fasciata. 



A knowledge of the following facts are necessary to understand 

 the application of the prophylactic measures which are now 

 employed. The Yellow Fever patient is only capable of infecting 

 the Stegomyia during the first few days of the onset of the disease, 

 the period usually given is the first three days, although the French 

 authorities extend the infective period. The Yellow Fever cadaver 

 is non-infectious ; in consequence the separate burial ground for 

 Yellow Fever cases is needlessly harsh, quite unnecessary and un- 

 scientific. At no stage can the Y el low Fever patient or the cadaver 

 infect man directly. In common with many other non-immunes I 

 was almost daily in the Yellow Fever Emergency Hospital examining 

 patients and assisting at post mortems, but no case of infection ever 

 occurred amongst us. The well-screened Emergency Hospital, 

 although crowded with patients and extremely hot, was, nevertheless, 

 one of the safest places in New Orleans, because the Stegomyia was 

 effectively shut out. No case of direct transmission from the patient 

 to man has ever been recorded. The only one means is through the 

 mosquito, as Ross also proved in the case of Malaria. 



When the Stegomyia has taken a meal of blood from a patient 

 in the infective stage it is not at once capable of transmitting by its 

 bite the virus to a healthy individual. A very definite 7tumber of 

 days must elapse before the mosquito is itself infective, and capable 

 of transmitting the virus ; approximately this period is twelve days. 



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 mosquitoes were not destroyed. 



