When someone is first exposed to the EBV after childhood, they may contract the symptoms of mono, however more than half of them may show much milder symptoms or may have no symptoms at all. The symptoms of full-blown mono may include:
- fever
- fatigue
- malaise
- weakness
- headache
- bad sore throat, with characteristic creamy-looking pus covering the tonsils
- swollen lymph nodes in your neck and armpits
- swollen tonsils
- skin rash
- loss of appetite
- swollen spleen
- night sweats
- muscle aches or stiffness
The virus typically has a long incubation period (period before symptoms appear) of four to six weeks in adolescents and young adults. After the onset of symptoms, some may improve after only a week or two, such as the sore throat and fever, but the fatigue, enlarged lymph nodes, and swollen spleen may last for a month or longer.
When children are first infected with EBV between the ages of four and fifteen, the virus may cause a mild illness that resembles a common respiratory infection such as a common cold or sore throat, or may cause no symptoms at all. If first exposure to EBV occurs in older adults, mono can cause more severe symptoms and lasts longer.