It depends. One of my children rarely gets ill, and when she has, she has always recovered quickly, including very short lived fevers. She takes after her dad. My other child is like me: picks up pretty much everything. Like many children, that one sometimes recovers quickly, but many times not. For her and I, we take vitamins (just multi), and probiotics particularly leading up to a trip and during the trip, since they seem to help.
I have also been known to keep that younger-prone-to-illness child away from school/daycare/parties if it makes sense, and if they are young enough to get away with that.
Good luck - since that child may not have encountered yours on Monday, and may have been most contagious over the weekend, you may be ok-I hope so! Keep looking forward to your trip!