A patient complains that, for the past 3 days, he has had a headache, fatigue, loss of appetite,…

A patient complains that, for the past 3 days, he has had a
headache, fatigue, loss of appetite, muscle aches, swollen lymph glands, and a
sore throat. He also complains of mild tenderness in the left upper quadrant of
the abdomen.

 What illness is likely to cause these symptoms?