It took until Sunday evening, but I think the 'SphereFlu caught me then. The doctor confirmed it Tuesday; luckily, because it was within 48 hours, I could take Tamiflu (boy is that stuff expensive!). Finally, by Wednesday evening, I was feeling at least OK. I'm still pretty tired but at least am able to do some work (from home, luckily).
Now I just have to get healthy and keep the rest of the family healthy so we'll be ready for vacation at the end of next week.