I play tournament badminton and having fever after a tournament or even longer games is standard for me. I get high body temperature, sore throat, clogged nose and all flu-like symptoms. Have to get under a warm blanket or wear a pullover cos of the cold. The symptoms stay only until night, and next morning they're gone.
I eat properly during longer game sessions and take sugary drinks, as it is a must to be able to play for over 2 hours. The elevated temperature is something that simply seems to follow, hasn't changed during my level has gone higher, rather the opposite, things get more and more intense. Badminton is very intense exercise where you go with maximum intensity and cardio almost all the time, and a really aching body is another steady reward. Sometimes can hardly walk to the bus, it can be so heavy on the feet and also the back, the arm... often feel like the whole body is on fire, and in addition get the fever.
A doctor told me it is normal and a result from micro damages to the muscles in intense training. The body sort of thinks that muscles are damaged and raises the temperature to fight microbes. I haven't gotten any muscle damages, apart a torn tendon that was recently operated but that's a different story. Otherwise my muscles are doing fine.