not sure how to prevent it but it does appear quite suddenly, and includes a sore throat (gargle with salt water or straight peroxide, eat honey straight ,drink hat fluids).
Feeling lousy (rest, relax, fluids). may have chills, headaches, nausea, vomiting, and a rapid heart beat.
The throat is red and sore, swollen tonsils (if still have them) neck lymph nodes could be tender and enlarged.
However in about 2 wks it get better,,,, ,even without treatments, But antibiotics do help shorten the duration.
The only way is to avoid any one with the illness.