What Happens When You Have Mononucleosis?

Medically Reviewed on 2/16/2022
Once infected with mononucleosis, the virus may remain dormant in the throat and body fluids for the rest of your life.

Mononucleosis is a contagious viral infection usually caused by the Epstein-Barr virus (EBV). It typically affects adolescents and young adults and is characterized by symptoms such as fever, sore throat, swollen lymph nodes, and fatigue.

Symptoms typically resolve within two to four weeks of infection. However, the virus may remain dormant in the throat and body fluids for the rest of your life and may reactivate periodically with no obvious symptoms.

Most people are exposed to the virus by the time they reach middle age. If exposure occurs in childhood, symptoms may or may not develop, and the virus may remain inactive in their system throughout their lives. Infection can be transmitted despite the absence of symptoms.

Symptoms typically develop gradually, within four to six weeks (incubation period) after the person is infected with EBV and include:

Once a person is infected with mono, it is very unlikely that they will get the infection again. They will remain immune to the virus for the rest of their life.

What is mononucleosis?

Mononucleosis (mono) is an infectious viral disease caused by the Epstein-Barr virus (EBV) although other viruses can cause the disease too.

EBV is a type of virus called gamma herpes virus. It infects only humans and is the most common cause of infectious mononucleosis.

Mononucleosis is a contagious disease (spreads from person to person) that predominantly affects teenagers and young adults.

It is estimated that at least one out of every four people infected with EBV will eventually develop infectious mononucleosis.

Is mono easily transmitted?

Mononucleosis is also called “kissing disease” because the virus is easily and often transmitted by kissing and through saliva, other body fluids such as blood (transfusions) and semen (through sexual contact), and organ transplantations.

Additionally, it can be transmitted by:

  • Sharing glasses, cups, straws, or anything else with saliva on it
  • Sneezing and coughing

A person is contagious regardless of whether they have symptoms.

Although controversial among health experts, it is speculated that people can remain contagious and infect others even after the symptoms are gone or even months thereafter.


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How is mononucleosis diagnosed?

Infectious mononucleosis is typically diagnosed based on symptoms presented by the infected person.

Your doctor may recommend the following to judge the severity of infection:

Although not recommended routinely, certain laboratory tests (antibodies to Epstein-Barr virus [EBV]-associated antigens) can help distinguish recent or past infections.

  • Anti-viral capsid antigen (VCA) antibody tests:
    • Anti-VCA IgM: Typically appears in the early phase of EBV infection and disappears in four to six weeks after the infection is resolved.
    • Anti-VCA IgG: Initiates to appear in the acute phase, reaches its peak during the illness (four to six weeks), declines gradually, and remains persisting for the rest of the life.
  • Monospot test or heterophile test: It looks for a special type of antibody called heterophile antibodies that are produced in response to EBV infection.
  • EBV nuclear antigen (EBNA): Antibodies to EBNA are confirmed by immunofluorescent test, two to four months after the onset of symptoms and persists for the rest of life.
  • Early antigen (EA): Anti-EA IgG typically occurs in the acute phase of infection, a sign of active infection, and declines to undetectable levels post three to six months of initial infection.

Other than clinical interpretation, based on EBV antibody test, diagnosis of mononucleosis can be categorized into three types:

  1. Susceptible to infection: A person is considered susceptible to EBV infection if antibodies are absent to VCA.
  2. New or recent or current infection:
    • A primary EBV infection is confirmed by:
      • The presence of anti-VCA IgM and absence of antibody to EBNA.
      • High or rising levels of anti-VCA IgG and absence of antibody to EBNA after at least four weeks of illness.
  3. Past infection: A past infection of mononucleosis is suggested by the presence of antibodies to both VCA and EBNA.

How is mononucleosis treated?

Most people feel better in two to four weeks. However, for some, fatigue can remain for several weeks after the initial infection. Very rarely, symptoms may linger for six months or longer.

No vaccines are available yet to prevent the infection. However, you can protect yourself and prevent the infection if you avoid coming in close contact with the infected person.

If symptoms are mild, you can follow these simple measures to help relieve the symptoms:

If symptoms do not improve or get worse, consult healthcare personnel.

Complications of infectious mononucleosis

Very rarely, infectious mononucleosis can cause serious complications such as:

  • Hemolytic anemia
  • Inflammation of the kidney
  • Hepatitis (inflammation of the liver)
  • Liver failure
  • Jaundice (yellowing of the skin and eyes)
  • Spleen rupture
  • Inflammation of the heart
  • Upper airway obstruction
  • Abnormal heart rhythm
  • Nervous system disorders such as meningitis and encephalitis
Medically Reviewed on 2/16/2022
Image Source: iStock Images

About Infectious Mononucleosis Centers for Disease Control and Prevention: https://www.cdc.gov/epstein-barr/about-mono.html

Infectious Mononucleosis Johns Hopkins Medicine: https://www.hopkinsmedicine.org/health/conditions-and-diseases/infectious-mononucleosis

Infectious mono Doctors of Osteopathic Medicine: https://findado.osteopathic.org/infectious-mono-kissing-disease

Elena Ben-Joseph Mononucleosis KidsHealth: https://kidshealth.org/en/teens/mononucleosis.html