554 WALTER KEED. 



This experiment indicates at once the uselessness of destroying vahi- 

 able property for fear of infection. Had the people of the United 

 States known this one fact a hundred years ago an enormous amount 

 of money would have been saved to householders. 



Besides the experimental cases caused by mosquito bite, four 

 nonimmunes were infected by injecting blood drawn directly from 

 the veins of yellow-fever patients in the first two days of the disease, 

 thus demonstrating the presence of an infectious agent in the blood 

 at this early j^eriod of the attack. 



Even the blood serum of a patient, passed through a bacteria-proof 

 niter, was found to be capable of causing yellow fever in another 

 j)erson. 



The details of the experiments are most interesting, but it must 

 here suffice to briefly sum up the principal conclusions of this admi- 

 rable board of investigators, of which Reed was the master mind: 



1. The specific agent in the causation of yellow fever exists in the blood of 

 a patient for the first three days of his attack, after which time he ceases to 

 be a menace to the health of others. 



2. A mosquito of a single species, Stegomyia fafic'tata, ingesting the blood of 

 a patient during this infective period is powerless to convey the disease to 

 another person by its bite until abotit twelve days have elapsed, but can do so 

 thereafter for an indefinite period, probably during the remainder of its life. 



3. The disease can not in nature be spread in any other way than by the bite 

 of the previously infected Stegomyia. Articles used and soiled by patients do 

 not carry infection. 



These conclusions pointed so clearly to the practical method of 

 exterminating the disease that they were at once accepted by the 

 sanitary authorities in Cuba and put to the test in Habana, where for 

 nearly a century and a half by actual record the disease had never 

 failed to api:)ear annually. 



In February, 1901, the chief sanitary officer in Habana, Maj. W. C. 

 Gorgas, Medical Department," U. S. Army, instituted measures to 

 eradicate the disease, based entirely on the conclusions of the commis- 

 sion. Cases of yellow fever were required to be reported as promptly 

 as possible, the patient was at first rigidly isolated, and immediately 

 upon the report a force of men from the sanitary department visited 

 the house. All the rooms of the building and of the neighboring 

 houses were sealed and fumigated to destroy the mosquitoes present. 

 Window and door screens were put up, and after the death or recov- 

 ery of the patient his room was fumigated and every mosquito de- 

 stroyed. A war of extermination was also waged against mosquitoes 

 in general^ and an energetic effort was made to diminish the number 

 bred by draining standing water, screening tanks and vessels, using 

 petroleum on water that could not be drained, and in the most sys- 

 tematic manner destroying the breeding places of the insects. 



