Excellent point! Let me see what I can find. Until then I did find this...

The Acutes are "less ill" then the Chronics.

The Chronic category is again subdivided into three groups:
  1. the Walkers (these are those who still can walk, for example Chief Broomden)
  2. the Wheelers (those in a wheelchair)
  3. the Vegetables (paralytic patients).