The mystery was solved when we woke up Wednesday morning to find a sick little boy, complete with nausea, a stuffy nose, and nasty cough. He stayed home from school all day Wednesday and then tried to return Thursday, lasting all of 15 minutes (I dropped him off at 8:45am and he called from the school office at 9:00am saying he wasn't feeling well enough to stay). This morning he woke up feeling a whole lot better, though still not 100%.
In the meantime, insulin dosage seems to have to returned to normal. We've been monitoring closely, but BG levels have returned to "normal" at his regular pump settings. Thinking back, I can't recall having experienced this before, where insulin dosage increased by 50% in the couple of days leading up to an illness, but then returned to typical amounts during the illness. Anyone else noticed this before?