Prisoner of War mortality rates seem to be low overall around the Napoleonic era.

One source states both British and French rates were under 10%. Another acknowledges that the rate in the hulks was higher than in the prisons and that the prison rate was lower than that of the Royal Navy.

I imagine that the greater the numbers held, crammed into inadequate facilities the greater the spread of diseases and resultant deaths.

For comparison during the late 1770s to early 1780s the yearly prisoner of war mortality rates in Britain were Americans 1.5%, French 0.3%, Spaniards 1.8% and Dutch 0.6%. Number of prisoners held not stated.

Only because numbers are readily available, the mortality rates for the American Civil War:

Federals held in Confederate Prisons: 9% to 15.5%

Confederates held in Federal Prisons: 12%

Federals held in Andersonville: 29%

Confederates held in Elmira: 24% to 32.5%

Andersonville is considered the worst Confederate prison while Elmira is considered the worst Federal prison. Andersonville Prison, Georgia, existed from February 1864 to April 1865. 33,000 prisoners were held there and in September all well prisoners were move to another prison. Elmira Prison, New York State, was established in May 1864, so existed for only a year. 10,000 prisoners were held there.

Good hunting.

Ron