Hmmm...I haven't faced that problem. I am pretty open about my illness, it is a big part of my life and who I am. You could tell them that you aren't working right now due to some medical issues or just not working right now and leave it at that. As someone said, many people are out of work these days. Since being out of work can be such a sensitive subject for anyone, that would probably make them so uncomfortable they would move on to talk about something else.