I had Scarlet Fever when I was 24 and just starting in daycare....actually called in sick with it on my first full day. I felt very, very rough for 2 days, then started to get back to myself. My fever first day was 105.1 and would drop to 103 with meds, then spike again when they wore out. Next day was around 103.5-104. Third day was significantly reduced...not normal but getting there...but still kind of felt like I'd had the stuffing knocked out of me, but much better than before. Even with antibiotics, I'd be more inclined to take an extra day. Not so much because of the contagious factor, but because your son may still be feeling really, really rough. Maybe it hits adults harder, but I can say that I've never, ever been sooooo sick before or since. It was quite something.