Aww ummmm! There are varying degrees. I had viral pnueumonia over my A levels and came through it fine though I was a lot younger at the time.
I was pretty much ok the day before, felt a bit off and thought it was hayfever then woke up the next morning and could hardly sit up or open my eyes and big problems breathing, mum called the Dr out and I was ambulanced to hospital.
He's in the best place and they should have been able to get him started on treatment straight away.
Let us know how he gets on.