Hello, It is caused by the Epstein-Barr virus (EBV). It typically occurs in teenagers, but you can get it at any age. The virus is spread through saliva, which is why some people call it “the kissing disease.” The symptoms include: 1-fever 2-a sore throat 3-swollen lymph glands in your neck and armpits 4-a headache 5-fatigue 6-muscle weakness 7-swollen tonsils 8-night sweats If your symptoms don’t improve after one or two weeks of home treatment such as resting, getting enough fluids, and eating healthy foods, see your doctor. Hope I have answered your query. Let me know if I can assist you further.