Flu and (no) fever

Got some kind of a stupid flu: really sore throat, and hard to breathe while lying down (not hard to breathe in any medical emergency sense, just unpleasant enough to keep me awake all night). No other symptoms.

I find it weird that I almost never have a fever nowadays. Maybe once every several years. Didn't use to be that way - until 15 years ago or so I tended to have a low-grade fever with almost every flu. I think it's me who changed and not the flu viruses, because a lot of other people still seem to have a low-grade fever with almost every flu.

I wonder what causes changes like that. Not that I miss the fever, but when I was a kid and being above 37.3 meant being allowed to stay home instead of going to school, I would have been pissed off if I ran out of fevers.

Luckily I am an adult now and can stay home because of other flu symptoms just as well. In fact, what am I doing here at work today?