The loss of many lives to yellow fever during the 1898 Spanish American War prompted an investigation into how people caught the disease. Major Walter Reed is credited with proving, through a series of experiments with volunteers, that mosquitoes, not contaminated objects, are to blame.
It started with a single gunshot. Next, the air was raked with rifle and cannon fire, leaving the field strewn with wounded and dead. Army medics raced out under fire, rescuing comrade and enemy alike, patching their wounds, and moving them to field hospitals for further treatment.