That was only the start. Pain and touch provide the boundary of the self. Once that goes, people lose the instinct for self-protection. Brand recognised that the real damage was done not by the disease itself, but by the injuries that resulted.
The horror of leprosy was that it was visible: the bloated face, the parched skin, the fingers and toes gradually eaten away. There was no hiding it, and people feared contagion. Once it was identified, exclusion inevitably followed.
A square hut on stilts with large windows on all sides is pictured in Tony Gould's Don't Fence Me In. The caption identifies it as an o`bservation tower, and the reader is immediately put in mind of prison camps and armed guards. But this tower had a different function, to allow the able bodied inmates of America's most famous leprosarium, 80 miles from New Orleans, to climb up and look outwards to the Mississippi. There they could "dream of the big wide world beyond the barbed wire, where people were as free to come and go as the ships on the river".
Carville was a beautiful place, if you ignored the swampy patches, with its huge oaks, yellow-pink rain trees and profusion of songbirds. "It should have been a tonic to the soul," wrote Stanley Stein, the Carville crusader who did more than anyone to end the isolation endured by patients such as himself. "Except that we were fenced in."
What made leprosy a dread diagnosis was that it was a social as well as medical disease. The condition set people apart not as unwell, but as unclean. In this, it resembled Aids in the early years of the epidemic, when ignorance and prejudice led to the persecution of sufferers, many of whom were driven, like people with leprosy a century earlier, from jobs and homes.
Like Aids, leprosy was seen as a moral condition, a punishment for sins committed. It was often characterised as dirty or venereal. Yet although the popular image of the medieval "leper" is of a hooded cloaked figure with his bell and dish for alms, an outcast and beggar, for some good people leprosy represented a religious vocation rather than an affliction.
The missionary involvement with the disease is one of the themes of this engrossing book. As Stanley Stein wrote, "there is no mission to the tubercular, no mission to the diabetics, no mission to syphilitics.... there seems to be some special reward for working with `lepers'."
It is a story peopled with ordinary characters in extraordinary circumstances, driven to the heights and depths, and told with great narrative verve. Gould confesses that the book almost did not get written because he was afraid of being typecast as a medical historian after his earlier account of his own disease - polio - in A Summer Plague. Fortunately, he was quickly gripped and we can now share his fascination.
There are still a handful of people with leprosy living at Carville, although it was formally closed in 1999. New cases still occur in the US, mostly among immigrants, but a few still erupt from among the indigenous population of the Southern states. Britain's equivalent, St Giles at East Haningfield in Essex, closed in the 1980s. Today people with leprosy can be treated with drugs as outpatients. Provided the condition is not far advanced, it can be cured.
But the story of this "merciless disease" - "the hundreds of thousands of hearts it has broken, the agonising loneliness and misery left in its wake" - contains lessons that should not be forgotten.
Jeremy Laurance is Health Editor of `The Independent'