So you would be ok sitting next to a vomiting feverish child for eight hours? There is a reason trip insurance exists and this is the reason. For around $125 you can insure your trip so you lose nothing if you have to change or cancel. If you can't afford to change a trip last minute it's foolish not to have insurance. It's cruel to bring a vomiting child onto a plane, for the child an everyone around them. Cutting molars is not vomiting. And there is a nasty stomach big going around parts of the us. So it may not be "just strep". Not to mention "just strep" can have complications like Scarlett fever, not something you want to deal with on vacation. But hey, its really all about you isn't it.
Not thrilled - but you're handling money, touching the seats on the airplane, breathing in the airplane air - you're exposed to germs all day long! Many illnesses are very contagious before you even develope symptoms.
You could get on a plane (or go anywhere else) thinking you're fine and boom! Some stomach bug can hit you out of nowhere!
You do what you can - eat well, get rest and wash your hands often!