The 5-cent Famous American Scientists stamp, issued April 17, 1940, commemorates Dr. Walter Reed (1851-1902). A U. S. Army physician, Reed took a special interest in contagious and infectious diseases. He participated in research that linked flies to the spread of typhoid fever. When placed in charge of research on yellow fever, the principal cause of death of American soldiers in Cuba, he observed that family members and caregivers of yellow fever patients often did not contract the disease. He speculated that it might be spread by mosquitoes and performed experiments involving controlled exposure to the insects that proved the theory. A subsequent program of mosquito eradication led to the eventual minimization of the disease.