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Symptoms and Signs of Infectious Mononucleosis (Mono)

Doctor's Notes on Infectious Mononucleosis (Mono)

Infectious mononucleosis (often termed mono) is a disease most often caused by a virus. Symptoms and signs include chills, followed by fever, sore throat (often severe), enlarged tonsils, swollen lymph glands especially in the neck, muscle aches, headaches and severe fatigue. Some may develop a measles-like rash, jaundice and tiny spots resembling bruises inside the mouth. Abdominal soreness may indicate development of an enlarged spleen. Most of these symptoms usually last about 2 to 4 weeks and gradually resolve but some patients may exhibit symptoms of fatigue for months or even years.

The cause of infectious mononucleosis is most frequently due to an infection by the Epstein-Barr virus or less commonly, cytomegalovirus (CMV) or other pathogens. People can remain contagious for up to six months after infection; also, the viruses become dormant and if the patient’s immune system is weakened, viruses may be reactivated and then transmitted to others.

Medical Author:
Medically Reviewed on 3/11/2019

Infectious Mononucleosis (Mono) Symptoms

The most common symptoms of mononucleosis are fever, sore throat, swollen lymph nodes, and fatigue. Symptoms usually develop between four to six weeks after exposure to the EBV. Other signs and symptoms of mononucleosis may include the following:

In younger children, the symptoms may be more subtle and may additionally include irritability and poor feeding.

Infectious Mononucleosis Symptoms and Signs
Infectious Mononucleosis Symptoms and Signs

Infectious Mononucleosis (Mono) Causes

The Epstein-Barr virus causes mononucleosis in the majority of cases. This ubiquitous, highly contagious organism is a member of the Herpesviridae family of viruses (other viruses in this family include herpes simplex, varicella-zoster, cytomegalovirus, and human herpes virus 6 & 7). Cytomegalovirus (CMV) can sometimes also cause an illness with the symptoms of mononucleosis.

  • Mononucleosis most often occurs in people between 5-25 years of age, with the highest occurrence rate between 15-25 years of age.
  • A small percentage of college students contract mononucleosis each year.
  • In developed countries, it most often occurs in those of higher socioeconomic status.
  • By adulthood, most people have had EBV infections.
  • Not all individuals exposed to EBV, however, develop the symptoms of mononucleosis.
  • Once infected, a person develops lifelong immunity to future infections from the disease.
  • EBV infection has been associated with the development of certain cancers, such as nasopharyngeal carcinoma and Burkitt's lymphoma.
  • EBV is transmitted through exposure to body fluids containing the virus (for example, saliva).
  • EBV spreads most often via saliva (hence the name "kissing disease").
  • EBV also spreads through blood and genital secretions.

Symptoms of Mono Infectious Mononucleosis Treatment Slideshow

Symptoms of Mono Infectious Mononucleosis Treatment Slideshow

Infectious mononucleosis is a common infection caused by the Epstein-Barr virus (EBV). It is also known as glandular fever, the kissing disease, and mono. Symptoms of infectious mononucleosis include fatigue, sore throat, fever, and swollen lymph nodes. There is no treatment for mono, but supportive care involves resting and drinking plenty of fluids. The illness resolves without treatment, but symptoms may last from several weeks to months.


Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.