Diseases were the silent killers during the Civil War.  With so many soldiers gathered in such small areas with generally unsanitary conditions, diseases were able to spread rapidly. There were a whole host of them but the worst of all was by far Dysentery caused by contaminated water. This disease alone accounted for around 100,000 deaths on both sides.  Other common diseases were Typhoid, Malaria, Tuberculosis and Pneumonia.

Measles which killed William Depew also killed around 11,000 soldiers total. Not as many as other diseases, but Measles had its fair share. About 1 in 20 people who got this disease died as a result of it.

Unfortunately, the biggest thing that all of these Civil War diseases had in common was the fact that at the time nobody had any idea how to cure them.