dear bindersbee, i'm no expert, but i would say that you don't need to worry because i'm sure you lost all that weight during your illness (glad it's over now!
) mostly because you were practically dehydrated, which is very common for a flu, so you lost your water and now that you started eating normally and 'restoring' your sodium, the water is coming back, adding to your weight. another thing is that your body must have felt like it's starving and maybe went to 'starvation mode', now trying to catch up where it left of and holding on to the food you eat now.
i've been there quite a few times, so now i know if i don't eat enough for a few days and lose too much weight, it'll all come back as soon as i start eating normally. i usually just continue eating my usual meals and wait - in a few days, things go back to normal. so let's say you'll go back to where you were before the flu, and that's fine, in my opinon.
so, don't worry, just go back to your program and be patient, i'm sure it will be fine!