Thanks all - but I'm not "complaining" that the gift of health is or is ont curing me, more that I am getting a hell of a lot of commanders diseased when it isn't even time for their bedtime never mind old age or anything like that.
Its not happening in the same place so it isnt site based or anything. Maybe I am just being real unlucky.
There are several sites that cause disease in units. Most of them are death sites, but here are one or two blood sites as well. If you have one of those sites in the province in question, your commanders will get diseased despite GoH, though it will also remove the disease sooner or later and then the site will just put it back in. Relocate.