Singing while sick: Yes or no?

I recently purchased the HTS course, but I can't get started becuase I'm ill with a sore throat and and having difficulty taking full breaths.  I should be on the mend in a couple more days, but I've lost a week's worth of practice time and had to cancel a work session with the guitarist I'm collaborating with.  We've got a recording session in two days, and I don't think I'll be ready for it.  And comments or suggestions regarding this?  I know that illness can affect us all from time to time, and I've seen professional singers such as Ozzy Osbourne take to the stage in obviously poor health and manage to pull it off, although perhaps taking it a bit easy.  I'd like to know more about how to make the best of this bad situation.  Thanks!