M: Hi, Lynn, how are you feeling
W: Steven! Why How do you know
M: You were absent today. Tom told me that you had been iii. What’s wrong with you
W: Nothing serious. Yesterday I went to the supermarket after school. But it began to rain heavily on my way home. I was wet absolutely.
M: Bad luck.
W: This morning I got a fever. The doctor asked me to stay at home and have a rest after taking some medicine
M: Are you better now
W: Yes, I am much better now. I think I can go to school tomorrow.
M: That’s good.

Why did Lynn have a fever（）