Skip to content Skip to navigation
Skip to global navigation Menu

Health Service

Vassar College

Infectious Mononucleosis is caused by a virus. The Epstein-Barr virus (EBV) that causes mononucleosis is a type of herpes virus. Peak incidence of infection has been described in the 15 to 24-year age range. The virus is spread through contact with the saliva of another person who has the virus, although that person often is not acutely sick at that time. Kissing and contact with hands or toys soiled with infected saliva are common ways to spread the virus. It is shed in the saliva during the illness and on and off for many months after infection. The virus can reactivate later and be shed again to infect another person.

Symptoms may include

  • Fever
  • Sore throat including tonsillar enlargement with white patchy exudate
  • Swollen glands (especially in the back of the neck)
  • Fatigue
  • Lack of appetite and abdominal fullness

Symptoms start 30 to 50 days after exposure to the virus. Many people (especially infants and young children) develop mononucleosis and only have mild symptoms similar to the common cold. Older children and young adults are more likely to have significant symptoms. By the time many adolescents reach college, they have already had mono, albeit usually a mild case. Symptoms can last from one to several weeks.

Medical Attention

Although no treatment other than rest is needed for most people with mononucleosis, complications can develop and need medical attention. These include swelling of the throat enough to make it difficult to swallow or breathe, abdominal pain, rash, bleeding, or persistent high fevers.