"As long as we remember them ..."

From The Oxford Companion to American Military History

Until well into the 20th century, disease, rather than the effects of enemy weapons, was the the single most important producer of casualties.

Percentage of disease casualties to overall:

Revolutionary War: 90%
Civil War: 71%
Spanish America War: 30%
WWI: 16.5%
WWII: .6%

Note the significant drop between 1865 and 1917. The vaccine for typhoid, also called the soldier's disease, was developed in 1898. In 1911 the entire US military had been vaccinated for it.