Disease was rife in any large assembly of soldiers or prisoners. Medical knowledge wasn't what it is today. Doctors were needed at the front and in medical hospitals. Heating cost and sanitation much money at a time when the army was the top priority.
Even with good heating, those who weren't accustomed to Northern climates would suffer. So far as I know, though, you didn't see men reduced to ragged skeletons in Northern prisoner of war camps as they were at Andersonville.
And the North treated black refugees fleeing slavery with savage indifference, and overt hostility, bordering on genocide.
Compared to what? Compared to slavery? Providing for thousands of runaway slaves can't have been easy. Still, they were fed and housed and even taught to read and write. I'd go easy with the "genocide" if I were you.
More ex-slave refugees died of disease, exposure and starvation (@ 400,000 total) than soldiers died on either side from any cause (250,000 CSA, 350,000 Union). Union neglect of ex-slaves fleeing behind their lines was at least as lethal as Civil War combat to both sides combined.
Sick From Freedom explains this in detail. Or read the review at the Journal of Military History.
Better, buy the book from Amazon - the Kindle edition is only $12.09, and you can read it on your computer with the free Kindle application.
Absolutely true. More men died from 'camp disease' in the Civil War than from combat. Measles, mumps, etc. that young men from the farms who had never ventured more that 20 miles from their birthplace with no acquired immunity suddenly thrust into camps with thousands of other people. The diseases ran rampant.
Medical knowledge wasn't what it is today.
Again totally true. But they knew very well then that you don't build latrines upstream of a drinking water supply. That was well known but exactly the situation that existed at Andersonville, and exactly the cause of the high mortality rate there. It was dysentery that killed thousands, entirely preventable, well understood at the time, and entirely the result of intentional neglect on the part of the camp commanders.