Sorry, didn't mean to worry you, but I caught a vomit bug 4 days after DS had it, so I always feel I cannot relax a little until around day 5!
Your DS may well escape the bug though, so don't worry too much.
My entire family came down with a severe vomit bug last year & I somehow totally escaped it, despite being up to my elbows in vomit drenched sheets, pjs, teddies etc!