I usually do take the sibling and it usually comes back to bite the parent in the butt because child takes longer to get sick and parent is off 3 days with first and then 2 with second instead of letting them get it right away and off only 3-4 days.

I also don't find a lot of illness moves from sibling to sibling but at the same time I take my own precautions at daycare and for those two days I am on top of the sibling about stuff in the mouth, hand washing etc. I don't sweat the cleaning because I can't know for sure that it isn't one of the other kids that is actually closer to getting sick than the so far well sibling so an exercise in futility.