Hmmm...
I started feeling a bit 'off' last night. All of a sudden, I felt cold and had an ache in my joints, so I took a painkiller and went to bed. I had a reasonable night's sleep.
This morning, every joint in my body is painful - even in my fingers, although I'm not feeling cold any more. One more pain killer and I'll see if that makes me break out in a sweat. If it does, then I have a fever.
Not promising at all and I have to finish writing and testing code for a new back end subsystem by Thursday.