Mononucleosis (mono) is an infection caused by a virus. It is marked by fever, lack of energy, and swollen glands.
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Mono is caused by the Epstein-Barr virus (EBV). It is passed from person to person through contact with someone else's saliva, such as through:
- Intimate behavior, such as kissing
- Sharing food or drinks
Many people get EBV during their lifetime. Things that raise the risk that EBV will turn into mono are:
- Getting EBV after age 10
- Lowered immune system due to other illness, stress, or lack of energy
- Living in close quarters with many people, such as in a college dormitory
Getting mono once means a person will be immune to it in the future.
Signs of mono start 4 to 7 weeks after a person was exposed to the virus. The first symptoms may be a sense of weakness that lasts about 1 week. Next, a person may have:
- High fever
- Severe sore throat
- Swollen glands
- Lack of energy
- Loss of hunger
- Muscle aches
- Belly swelling
- Yellowing of the skin and whites of the eyes
The doctor will ask about symptoms and past health. A physical exam will be done.
Blood tests may be done to look for signs of infection.
There is no way to cure mono or to shorten the length of the illness. It lasts 4 to 6 weeks, but the lack of energy may last longer.
The goal is to manage symptoms. Choices are:
- Lifestyle changes, such as limiting contact sports and heavy lifting to avoid injury to a swollen spleen
- Supportive care, such as getting rest, drinking plenty of fluids, and gargling with salt water
- Medicines to ease pain and swelling in the throat, such as pain relievers or steroids
To lower the risk of this problem:
- Avoid contact with anyone who has active mono.
- Do not share drinks or food with anyone who may be sick.
Centers for Disease Control and Prevention
National Institute of Allergy and Infectious Diseases
About Kids Health—The Hospital for Sick Children
The College of Family Physicians of Canada
Dunmire SK, Verghese PS, et al. Primary Epstein-Barr virus infection. J Clin Virol. 2018 May;102:84-92.
Ebell MH, Call M, et al. Does this patient have infectious mononucleosis?: The rational clinical examination systematic review. JAMA. 2016 Apr 12;315(14):1502-1509.
Epstein-Barr virus (EBV) infection. EBSCO DynaMed website. Available at: https://www.dynamed.com/condition/epstein-barr-virus-ebv-infection . Accessed October 28, 2020.
Mononucleosis. Family Doctor—Academy of Family Physicians website. Available at: http://familydoctor.org/familydoctor/en/diseases-conditions/mononucleosis.html. Accessed October 28, 2020.
Last reviewed September 2020 by EBSCO Medical Review Board James P. Cornell, MD Last Updated: 4/30/2021