TRANSMISSION OF YELLOW FEVER BY MOSQUITOES. 669 



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

 the temperature was 100.4° P., the pulse 98; at 1 p. m., 10L2° F., the pulse m and 

 his eyes were much injected and fac^e suffused. He was removed to the yellow-fever 

 wards. He was seen on several occasions by the Imar.l of experts an<l tl.e diagnosis 

 of yellow fever confirmed. 



The period of incubation in this case, dating from the first visit to "Building No. 

 2," was three days and twenty-tliree hours. If reckoned from his last vi.«it i't was 

 two days and eighteen hours. There was no other possible source for liis infection, 

 as he had been strictly quarantined at Camp Lazear for a period of thirty-two days 

 prior to his exposure in the mosquito l)uilding. 



During each of Moran's visits two noninnnunes remained in this same building, 

 only protected from the mosquitoes by the wire-screen partition. From December 

 21, 1900, till January 8, 1901, inclusive— eighteen nights— these noninnnunes have 

 slept in this house, only protected by the wire-screen partition. These men have 

 remained in perfect health to the i)resent time. 



Thus at Camp Lazear of 7 nonimmunes whom we attempted to infect ])y means 

 of the bites of contaminated mosquitoes we have succeeded in conveying the disea.«e 

 to 6, or 85.71 per cent. On the other hand, of 7 nonimmunes whom we tried to 

 infect by means of fomites, under particularly favorable circumstances, we did not 

 succeed in a single instance. 



It is evident that in view of our pre.sent knowledge relating to the 

 mode of transmission of 3'ellow fever, the preventive measures which 

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

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

 are either of no avail oi* 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 upo!i 

 the direct contact of the sick with noninmmne 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 

 responsible 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 harmless, as the experimental evidence now stiinds. 

 Yellow-fever epidemics are terminated by cold weather because then 

 the mosquitoes die or become torpid. The sanitary condition of our 

 southern seaport cities is no better in winter than in summer, and if 

 the infection attached to clothing and bedding it is difficult to under- 

 stand why the first frosts of autumn should arrest the progress of an 

 epidemic. But all this is explained now that the mode of transmission 

 has been demonstrated, 



Insanitarv local conditions may, however, have a certain influence 

 in the propagation of the disease, for it has been ascertained that the 

 species of mosquito which serves as an intermediate host for the 

 yellow-fever germ may breed in cesspools and sewers as well as m 

 stagnant pools of water. If, therefore, the streets of a city are 

 unpaved and ungraded, and there are open spaces where water may 



