I pondered the issue of illness and disability very early in the creation of Harry’s world. Did wizards catch colds? Could they cure illnesses that baffled Muggles? Were there disabled wizards? What were the limits of wizarding medicine, or could it fix anything?
Some of these questions went to the heart of the story, because the theme of death runs through every volume of the Potter books. Having decided that magic could not raise the dead (even the Resurrection Stone does not truly return the dead to life), I then had to decide what might kill a wizard; what kind of illnesses they could catch; what injuries they might sustain, and which of the last two could be cured.
I decided that, broadly speaking, wizards would have the power to correct or override ‘mundane’ nature, but not ‘magical’ nature. Therefore, a wizard could catch anything a Muggle might catch, but he could cure all of it; he would also comfortably survive a scorpion sting that might kill a Muggle, whereas he might die if bitten by a Venomous Tentacula. Similarly, bones broken in non-magical accidents such as falls or fist fights can be mended by magic, but the consequences of curses or backfiring magic could be serious, permanent or life-threatening. This is the reason that Gilderoy Lockhart, victim of his own mangled Memory Charm, has permanent amnesia, why the poor Longbottoms remain permanently damaged by magical torture, and why Mad-Eye Moody had to resort to a wooden leg and a magical eye when the originals were irreparably damaged in a wizards’ battle; Luna Lovegood’s mother, Pandora, died when one of her own experimental spells went wrong, and Bill Weasley is irreversibly scarred after his meeting with Fenrir Greyback.
Thus it can be seen that while wizards have an enviable head start over the rest of us in dealing with the flu, and all manner of serious injuries, they have to deal with problems that the rest of us never face. Not only is the Muggle world free of such perils as Devil’s Snare and Blast-Ended Skrewts, the Statute of Secrecy has also kept us free from contact with anyone who could pass on Dragon Pox (as the name implies, originally contracted by wizards working closely with Peruvian Vipertooths) or Spattergroit.
Remus Lupin’s affliction was a conscious reference to blood-borne diseases such as the HIV infection, with the attendant stigma. The potion Snape brews him is akin to the antiretroviral that will keep him from developing the ‘full-blown’ version of his illness. The sense of ‘apartness’ that the management of a chronic condition can impose on its sufferers was an important part of Lupin’s character. Meanwhile, Mad-Eye Moody is the toughest Auror of them all, and a man who was very much more than his significant disabilities.