On the evening of September 18, five days after the bite, Dr. Lazear complained of feeling "out of sorts," and had a chill at 8 P.M.
On September 19, twelve o'clock noon, his temperature was 102.4°, pulse 112; his eyes were injected and his face suffused; at 3 P.M. temperature was 103.4°, pulse 104; 6 P.M., temperature 103.8° and pulse 106; albumin appeared in the urine. Jaundice appeared on the third day. The subsequent history of this case was one of progressive and fatal yellow fever, the death of our much-lamented colleague having occurred on the evening of September 25, 1900.
Evidently in this case the evidence is not satisfactory as to the fatal attack being the result of the bite by a mosquito "while on a visit to Las Animas Hospital," although Dr. Lazear himself was thoroughly convinced that this was the direct cause of his attack.
The inference by Dr. Reed and his associates, from the experiments thus far made, was that yellow fever may be; transmitted by mosquitoes of the genus _Culex_, but that in order to convey the infection to a nonimmune individual the insect must be kept for twelve days or longer after it has filled itself with blood from a yellow fever patient in the earlier stages of the disease. In other words, that a certain period of incubation is required in the body of the insect before the germ reaches its salivary glands, and consequently before it is able to inoculate any individual with the germs of yellow fever. This inference, based upon experimental data, received support from other observations, which have been repeatedly made, with reference to the introduction and spread of yellow fever in localities favorable to its propagation. When a case is imported to one of our southern seaport cities, from Havana, Vera Cruz, or some other endemic focus of the disease, an interval of two weeks or more occurs before secondary cases are developed as a result of such importation. In the light of our present knowledge this is readily understood. A certain number of mosquitoes having filled themselves with blood from this first case after an interval of twelve days or more bite nonimmune individuals living in the vicinity, and these individuals after a brief period of incubation fall sick with the disease; being bitten by other mosquitoes they serve to transmit the disease through the "intermediate host" to still others. Thus the epidemic extends, at first slowly from house to house, then more rapidly, as by geometrical progression.