Signs and symptoms of mononucleosis may include: 
Fatigue
Sore throat, perhaps misdiagnosed as strep throat, that doesn't get better after treatment with antibiotics
Fever
Swollen lymph nodes in your neck and armpits
Swollen tonsils
Headache
Skin rash
Soft, swollen spleen
 The virus has an incubation period of about four to six weeks, although in young children this period may be shorter. The incubation period refers to how long before your symptoms appear after being exposed to the virus. Signs and symptoms such as a fever and sore throat usually lessen within a couple of weeks. But fatigue, enlarged lymph nodes and a swollen spleen may last for a few weeks longer. When to see your doctor If you've been experiencing the above symptoms, you may have mononucleosis. If your symptoms don't get better on their own in a week or two, see your doctor.