fever!

In Japanese English "fever!" means an excited state, generally in the context of something like pachinko gambling where you are on a winning streak.
However here it simply means higher-than-normal body temperature.
Tonchan had to come home early yesterday because she had a fever. Still does this morning.
Man, she is grumpy when she's sick.
The joke is she had chicken pox last week and was fine. Now, she's just got a cold or something and is pretty miserable.