Whenever illness strikes me, all previous logic regarding my blood sugars tend to get twisted upside down. Even though it's annoying the only thing that helps me is to focus on healing from the illness and avoid extra stress. Doing some testing/calculations to adjust my dosages tends to help temporarily but this can be a bit of a headache.
It could be a digestion issue if the food is taking a long time to have an impact on your blood sugar...or perhaps since you haven't been eating as much your body is using the carbs more efficiently? I wouldn't worry too much and just focus on rest/recovery, you'll be back in no time!
Best wishes