YELLOW FEVER AND MOSQUITOES. 237 



day, Dec. 9, 1900, twelve days; 4, a mild ease, on the first day, Dec. 13, 1900, 

 eight days; 7, a woll-markcd case, on the first day, Dec. IG, 1900, five days — 

 total, 15. 



Only one of these insects was considered capable of conveying the infec- 

 tion, \dz., the mosquito that had bitten a severe case twenty-four days before; 

 Avhile three others — the twelve-day insects — had possibly reached the dangerous 

 stage, as they had been kept at an average temperature of 82° F. 



At 12, noon, of the same day, John J. Moran — already referred to as Case 2 

 iu this report — a non-immune American, entered the room where the mosquitoes 

 had been freed, and remained thirty minutes. During this time he was bitten 

 about the face and hands by several insects. At 4.30 p. m., the same day, he 

 again entered and remained twenty minutes, and was again bitten. The follow- 

 ing day, at 4.30 p. m., he, for the third time, entered the room, and was again 

 bitten. 



Case 7. — On Dec. 25, 1900, at 6 a. m., the fourth day, Moran complained of 

 slight dizziness and frontal headache. At 11 a. m. he went to bed, complaining 

 of increased headache and malaise, with a temperature of 99.6° F., pulse 88 ; at 

 noon the temperature was 100.4° F., the pulse 98; at 1 p. m., 101.2° F., the pulse 

 90, and his eyes were much injected and face suffused. He was removed to the 

 yellow fever wards. He was seen on several occasions by the board of experts 

 and the diagnosis of yellow fever confirmed. 



The period of incubation in this case, dating from the first visit to 'Build- 

 ing No. 2,' was three days and twenty-three hours. If reckoned from his last 

 visit it was two days and eighteen hours. There was no other possible source 

 for his infection, as he had been strictly quarantined at Camp Lazear for a 

 period of thirty-two days prior to his exposure in the mosquito building. 



During each of Moran's visits, two non-immunes remained in this same 

 building, only protected by the wire-screen partition. From Dec. 21, 1900, till 

 Jan. 8, 1901, inclusive — eighteen nights — these non-immunes have slept in this 

 house, only protected by the wire-screen partition. These men have remained 

 in perfect health to the present time. 



Thus at Camp Lazear, of 7 non-immunes whom we attempted to infect by 

 means of the bites of contaminated mosquitoes, we have succeeded in conveying 

 the disease to 6, or 85.71 per cent. On the other hand, of 7 non-immunes whom 

 we tried to infect by means of fomites, under particularly favorable circum- 

 stances, we did not succeed in a single instance. 



It is evident that in view of our present knowledge relating to the 

 mode of transmission of yellow fever, the preventive measures which 

 have heretofore been considered most important, i. e., isolation of the 

 sick, disinfection of clothing and bedding, and municipal sanitation — 

 are either of no avail or of comparatively little value. It is true that 

 yellow fever epidemics have resulted, as a rule, from the introduction to 

 a previously healthy locality of one or more persons suffering from the 

 disease. But we now know that its extension did not depend upon the 

 direct contact of the sick with the non-immune individuals and that 

 isolation of the sick from such contact is unnecessary and without avail. 

 On the other hand complete isolation from the agent which is respon- 

 sible for the propagation of the disease is all-important. In the absence 

 of a yellow-fever patient from which to draw blood the mosquito is 

 harmless, and in the absence of the mosquito the yellow-fever patient is 



