It's going around (they sent home an info sheet from school) and now I think I have it. That would explain the sudden onset of red rash and aching knuckles, wrists, and knees. It's either fifth disease or too much knitting and squat-pressing. Hope has the rash, too, and Hank had a mysterious hand rash a couple weeks ago. I love it when the puzzle pieces all fall in place. So satisfying.