Twice a year I get this 24 hr flu-like virus thing

What is it? Twice a year, like clockwork. I'll feel tired and achy in the morning, and then a little dizzy, then flu-like shooting pains in arms, legs and fingers, and by the evening it's like a full-blown flu thing but without any sneezing or coughing or anything like that. Then I'll go to bed really early, have 12 hours of sweaty, delirious sleep in which my mind gets fixated on ridiculously nonsensical thoughts (this time I was convinced that my legs were a screaming 303 acid house bass line which my bed could not contain) and I go through a week's worth of laundry changing sweaty t-shirts every couple of hours, then I wake up the next day and feel absolutely fine. 

So I have two thoughts: one, that it's just some weird 24 hour bug that goes around, and two, that it actually is the flu but my body fights it off relatively quickly, before the wheezing and sneezing starts. 

Amazingly enough, that seems to be the case.