66-4 TRANSMISSION OF YELLOW FEVER BY MOSQUITOES. 



vided. Thene were i>la<.'ed at a distance of about 20 feet from each otlier, and were 

 numl)ered 1 to 7, respectively. 



Camp Lazear was established November 20, 1900, and from this date was strictly 

 quarantined, no one l)ein<j: permitted to leave or enter camp except the three immune 

 members of the detachment and the members of the board. Supplies were drawn 

 chiefly from Columbia Barracks, and for this purpose a conveyance under the con- 

 trol of an immune acting hospital steward, and ha\dng an immune driver, was used. 



A few Spanish inmiigrants recently arrived at the port of Havana were received 

 at Camp Lazear from time to time while these observations were being carried out. 

 A nonimmune ])ers(jn, having once left this camji, was not permitted to return to it 

 under any circumstances whatever. 



The temperature and pulse of all nonimmune residents were carefully recorded 

 three times a day. Under these circumstances any infected individual entering the 

 camp could be promptly detected and removed. As a matter of fact, only two per- 

 sons, not the subject of experimentation, developed any rise of temperature; one, a 

 Spanish immigrant with probable commencing pulmonary tuberculosis, who was 

 discharge<l at the end of three days, and the other, a Spanish innnigrant who 

 developed a temperature of 102.6 F. on the afternoon of his fourtli day in camp. He 

 was at once remove<l, with his entire beddmg and baggage, and placed in the receiv- 

 ing ward at Cohnubia Barra<'ks. His fever, which was marked by daily intermis- 

 sions for three days, subsided upon the administration of cathartics and enemata. 

 His attack was considered to be due to intestinal irritation. He was not permitted, 

 however, to return to the camp. 



No noninunune resident was subjected to inoculation who had not passed in this 

 camp the full period of incubation of yellow fever, with one exception, to })e herein- 

 after mentioned. 



For the purp(jse of experimentation subjects were selected as follows: From tent 

 No. 2, 2 noninmiunes, and from tent No. o, 'A nonimmunes. Later, 1 nonimmune in 

 tent No. 6 was also designated for inoculation. 



It should V)e borne in mind that at the time when these inoculations were begun, 

 there were only 12 nonimmune residents at Camp Lazear, and that 5 of these were 

 selected for experiment, viz, 2 in tent No. 2 and 3 in tent No. 5. Of these we suc- 

 ceeded in infecting 4, viz, 1 in tent No. 2 and 3 in tent No. 5, each of whom devel- 

 oped an attack of yellow fever within the period of incubation of this disease. The 

 one negative result, therefore, was in case 2 — ]\Ioran — inoculated with a mosquito 

 on the fifteenth day after the insect had bitten a case of yellow fever on the third 

 day. Since this moscjuito failed to infect ca.«e 4, three days after it had bitten Moran, 

 it follows that the result could not have been otherwise than negative in the latter 

 case. We now know, as the result of our observations, that in the case of an insect 

 kept at room temperature during the cool weather of November fifteen or even 

 eighteen days would, in all probability, be too short a time to render it capable of 

 producing the disease. 



As bearing upon the source of infection, we invite attention to the i)eriod of time 

 during which the subjects had been kept under rigid ({uarautine prior to successful 

 inoculation, which was as f(jllows: Case 1, fifteen days; case 3, nine days; case 4, 

 nineteen days; case 5, twenty-one days. We further desire to emphasize the fact 

 that this epidemic of yellow fever, which affected 33.33 per cent of the nonimmune 

 residents of Camp Lazear, did not concern the 7 nonimmunes occupying tents Nos. 

 1, 4, 6, and 7, but was strictly limited to those individuals who had been bitten by 

 contaminated mosquitoes. 



Nothing could point more forcibly to the source of this infection than the order of 

 the occurrence of events at this camp. The precision with which the infection of 

 the individual followed the bite of the mosquito left nothing to be desired in order 

 to fulfill the requirements of a scientific experiment. 



