YELLOW FEVER is an acute infections disease which is transmitted from the sick to susceptible individuals through the agency of mosquitoes. The yellow fever mosquito (Sug osnyus fa data) is found in tropical and semi nopical regions, and especially in lowlands um the sea or in river valleys. This serves as 'an intermediate host' for fever parasite, which is present in the blood of those sick with the disease during the first three days of the attack. After filling itself with blood from a yellow-fever patient a period of 12 days is required for the development of the parasite in the body of the mosquito before it can transmit the disease, by its sting, to ao other individual.
These facts have been established by the experiments of a board appointed upon the recommendation of the writer, in 1900, for the study of yellow fever in the island of Cubs. The late Maj. Walter Reed, surgeon United States of America, was president of this board. and the success attained is largely due to his carefully made plans and their intelligent and conscientious execution by himself and his associates.
In a 'preliminary note' read at the meeting of the American Public Health Association, 22 Oct. 1900, the board gave a report of three cases of yellow fever which they believed to be the direct result of 'mosquito inoculations.' Two of these were members of the board, namely, Dr. Jesse W. Lazear and Dr. James Carroll, who voluntarily submitted themselves to the experiment. Dr. Carroll suffered a se vere attack of the disease and recovered, btu Dr. Lazear fell a victim to the disease and to his enthusiasm in the cause of science and be mani ty. Fortunately no other deaths occurred during the subsequent experiments which Major Reed found it necessary to make in order to establish the fact that yellow fever is, beyond question, transmitted by mosquitoes of the gems SSegonsyia, and in no other way. In a report made in May 1901, Major Reed says: 'We have thus far succeeded in conveying racier fever to 12 individuals by means of the bites of contaminated mosquitoes.' These experiments were made upon individuals who volunteered to submit themselves to the mosquito inocubitiom with a full knowledge of the possibility of serer ous and even fatal results. of the vol
unteers were United States soldiers, and some were Spanish immigrants who had recently arrived in Cuba. Further experiments showed that blood drawn from 'a yellow-fever patient during the first three days of the disease and injected by means of a hypodermic syringe be neath the skin of a susceptible individual give, rise to a characteristic attack of yellow fever iu the inoculated individual But all attempts to demonstrate the specific infectious agent (yellow-fever parasite) in the blood or in the bodies of infected mosquitoes have been unsuc cessful. This is probably due to the fact that the yellow-fever parasite is so small as to le practically ultra-microscopic. This inference is supported by experiments made in Cnba by Assistant Surgeon James Carroll, United States of America, a member of the board heretofore referred to. Dr. Carroll found that when blood taken from the circulation of a yet/ow-fever patient was passed through a Berk' feldt flues a small quantity of the filtrate injected under the skin of a susceptible person gave rise to a typical attack of the disease.
The experimental results obtained by Major Reed and his associates have been fully con firmed by several independent investigators, including a board of experts from the Pasteur Institute of Paris, who were sent .o Brazil to make researches with reference to the etiology of this disease.
Having ascertained that yellow fever is transmitted from man to man by an intermediate host — mosquitoes of the genus Stegontyia, Major Reed and his associates conducted a series of well-planned experiments for the pur pose of ascertaining whether the disease may also be propagated, as has been commonly sup posed, by clothing, bedding and other articles which have been in use by those sick with the disease. The results of these experiments were entirely negative. That is, all efforts to com municate the disease to susceptible individuals through the medium of such articles were with out result.