Better health conditions would have changed the outcome of causes of death during the Civil War. It is indisputable that many soldiers died as a result of common occurrences that are easily treatable such as infection or easily treated diseases. Conditions during the time of the Civil War can't even compare to how good they are today.
Better medical care would not have changed the outcome of the civil war, because ultimately, the two sides would have fought each other until one of the sides won. There would have been continued fighting and ultimately the North would have been more successful in the end because they had more finances and better equipment.
No, better health conditions would not have changed the outcome of the American Civil War. Because the North had more funds, it would still have won. Better health conditions would have led to fewer deaths. A lot of people died from disease and illnesses due to conditions. But I don't believe the South would have won.
Both sides in the Civil War faced the same conditions, given that they were battling one another in the same locations. If there had been better health conditions, it would have benefitted both sides, therefore canceling each other out. The diarrhea didn't change the outcome of the Civil War in America.