I played poker when I had a temperature of 39 degrees. It's different from the usual game, I was always in a bad mood and felt like I was playing inadequately. When you're sick, you do almost nothing but take medicine and stay in bed, and poker saves you from this boredom.
Not all diseases have neurological disorders, so in theory you could, and if any disease causes an alteration in your consciousness, it is advisable not to, but it doesn't prevent you from doing so.
Hi.
I never start a game if I'm not feeling well. This makes no sense. I think that if you are sick, your chances of good results are significantly reduced.
I have played 'under the weather' but never with a fever. Obviously your mental capabilities are weaker, thus I can play in smaller volume and smaller stakes then usual. So its possible to play, its just that your game will suffer.