"The impact of disease on the course of the Civil War began almost as soon as the conflict was sparked. Both Union and Confederate soldiers found themselves caked in mud and sleeping in tents in improvised encampments. Without knowledge of how diseases spread, these close quarters encouraged bacteria and viruses to run rampant through the ranks. Measles, mumps, whooping cough and chickenpox ravaged the troops first while in training camps, spreading via exhaled respiratory droplets and aerosols from one soldier to the next as the germs found new paradise in the bodies of countrymen whose rural lives had largely isolated them from previous exposure. When the new soldiers finished training, they joined the armies in the field, where the so-called “camp diseases” of pneumonia, smallpox and the skin infection erysipelas quickly mounted a second wave of assault. “Theoretically, all recruits were to be vaccinated [for smallpox] coming into the army,” says Robert Hicks, PhD, former director of the Mütter Museum of The College of Physicians of Philadelphia and an expert in Civil War medical history. But in practice, he says, “that simply didn’t happen.” The Union enacted a blockade of all Southern ports early in the war, which limited the Confederates’ ability to import medical supplies. However, because every person at that time had an understanding of the power of disease, unprotected troops engaged in desperate attempts at home self-innoculations using pus from the oozing sores of infected friends and neighbors."