On August 1, the regiment moved four miles northeast from its post-battle camp near the Stone Bridge to Centreville.

A week later, illness had so overtaken the 13th that Pvt. Thomas D. Wallace of the Winston Guards wrote: “All of our regiment is sick at this time. There isn’t enough of us to wait on the sick and stand guard so we have no guards. We have the name of the ‘sick regiment’ now.”

Disease killed many more Civil War soldiers than weapons did, especially on the Rebel side—an estimated 75 percent of their 258,000 deaths. Many of them were country boys with little exposure to large numbers of people and they thus had not developed immunity to even such common childhood diseases as the measles.

So it’s not surprising that within days after First Manassas, many of the 13th Mississippi were stricken, and some dying, mainly with measles, but also bronchitis, “bilious fever,” diarrhea, pneumonia, and typhoid fever.

Within two weeks of the battle, the outbreak was almost epidemic.

Quartermaster clerk William H. Hill was recording deaths day after day, because he was ordering the building of the coffins.

“600 men of our regiment reported on the sick list this morning,” Hill wrote on Aug. 5. “Three of our regiment died today.”