It hasn't even been a full week since he was confirmed to be infected. No one has given it time for the worst to kick in.

This is not a fast moving virus. It's slow and takes time to really develop. By him bullying his way out of the hospital like this, refusing oxygen yesterday and generally being a dumbass about it, he's not doing himself any favors. Just watch and wait until later this week and by the weekend, he'll be right back in the hospital. I say give it about 2-4 weeks before it really takes him.