These first two paragraphs from General Marshall's Biennial Report concentrate on the number of casualties counted from December 7, 1941 up to June 30, 1945 (keep in mind that this immediate estimate would have to be adjusted as time advanced and more men would continue to die of the wounds inflicted during earlier periods of the war).
Here are last two paragraphs concerning the remarkably low amount of non-battle deaths suffered by the U.S. military during the course of the Second World War. General Marshall attributed this fact to the broad immunization program that was enacted on all fronts by the army medical corps.
"The comparison of non-battle death rate in this and other wars is impressive. During the Mexican War, 10 percent of officers and enlisted men died each year of disease; the rate was reduced to 7.2 percent of Union troops in the Civil War; tp 1.6 percent in the Spanish War and the Philippine Insurrection; to 1.3 percent in World War I; and 0.6 percent in this war".
Click here to read a news report on the American military casualties that were amassed from 1941 up to November, 1944.