The story of yellow fever illustrates one of the greatest practical triumphs of scientific medicine; indeed, in view of its far-reaching commercial consequences, it may range as one of the first achievements of the race.  Ever since the discovery of America, the disease has been one of its great scourges, permanently endemic in the Spanish Main, often extending to the Southern States, occasionally into the North, and not infrequently it has crossed the Atlantic.  The records of the British Army in the West Indies show an appalling death rate, chiefly from this disease.  At Jamaica, for the twenty years ending in 1836, the average mortality was 101 per thousand, and in certain instances as high as 178.  One of the most dreaded of all infections, the periods of epidemics in the Southern States have been the occasions of a widespread panic with complete paralysis of commerce.  How appalling the mortality is may be judged from the outbreak in Philadelphia in 1793, when ten thousand people died in three months.(5) The epidemics in Spain in the early part of the nineteenth century were of great severity.  A glance through La Roche’s great book(6) on the subject soon gives one an idea of the enormous importance of the disease in the history of the Southern States.  Havana, ever since its foundation, had been a hotbed of yellow fever.  The best minds of the profession had been attracted to a solution of the problem, but all in vain.  Commission after commission had been appointed, with negative results; various organisms had been described as the cause, and there were sad illustrations of the tragedy associated with investigations undertaken without proper training or proper technique.  By the year 1900, not only had the ground been cleared, but the work on insect-borne disease by Manson and by Ross had given observers an important clue.  It had repeatedly been suggested that some relation existed between the bites of mosquitoes and the tropical fevers, particularly by that remarkable student, Nott of Mobile, and the French physician, Beauperthuy.  But the first to announce clearly the mosquito theory of the disease was Carlos Finlay of Havana.  Early in the spring of 1900, during the occupation of Cuba by the United States, a commission appointed by Surgeon-General Sternberg (himself one of the most energetic students of the disease) undertook fresh investigations.  Dr. Walter Reed, Professor of Bacteriology in the Army Medical School, was placed in charge:  Dr. Carroll of the United States Army, Dr. Agramonte of Havana and Dr. Jesse W. Lazear were the other members.  At the Johns Hopkins Hospital, we were deeply interested in the work, as Dr. Walter Reed was a favorite pupil of Professor Welch, a warm friend of all of us, and a frequent visitor to our laboratories.  Dr. Jesse Lazear, who had been my house physician, had worked with Dr. Thayer and myself at malaria, and gave up the charge of my clinical laboratory to join the commission.

     (5) Matthew Carey:  A Short Account of the Malignant Fever,
     Philadelphia, 1793.