Lisa is in the eighth grade. Normally she is active in clubs, plays sports, and gets good grades, but lately she hasn't been feeling well. Her throat is sore and her lymph nodes feel swollen. She is running a fever and feels exhausted all of the time.
Lisa's doctor diagnoses her with
and tells her that although she can treat the fever, she cannot prescribe antibiotics
because Lisa's disease is viral. She recommends that Lisa forego sports and cut way back on her activities. She may not be able to go to school
for several weeks.

What did the doctor diagnose her with???