Symptoms of Mononucleosis

Mononucleosis ("mono") symptoms include a sore throat, swollen lymph nodes, fever, and fatigue. A cough and respiratory symptoms are less likely with viral infections such as mono. The lack of these symptoms can help differentiate mononucleosis from other infections with similar symptoms.

Mononucleosis—sometimes known as the "kissing disease"—is caused by the Epstein-Barr virus (EBV). EBV is most common during childhood when it produces few, if any, symptoms. In adolescents, teens, and young adults, EBV can cause symptoms that can last for weeks.

This article looks at common and uncommon signs of mononucleosis, including possible complications and treatments. It also explains when it is time to see a healthcare provider if you get mono.

mononucleosis symptoms
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Frequent Symptoms

The incubation period for mononucleosis (meaning the time between exposure and the appearance of symptoms) is four to six weeks, When symptoms appear, they tend to come on gradually, causing three to five days of non-specific symptoms like headache, fatigue, and malaise (a general feeling of unwellness).

Thereafter, the viral infection will manifest with classic symptoms like:

  • A severe sore throat
  • Fatigue and malaise that can persist for weeks and sometimes months
  • Swollen lymph glands, mainly in the neck and armpits but also sometimes in the groin
  • Swollen tonsils
  • Mild fever that can persist for weeks, often peaking later in the day
  • Aching muscles and joints
  • Nausea and stomach pain

An enlarged spleen (splenomegaly) can develop after two or three weeks in around half of all people. It may only be recognized during a physical exam and will eventually resolve without treatment.

Variations in Symptoms by Age

Different age groups experience mononucleosis differently. Children tend to be less affected by EBV and have few of the symptoms that adolescents and young adults do. Older adults often also lack more classic mono symptoms but are vulnerable to more serious complications.

Young Children

Before puberty, mononucleosis tends to cause mild flu-like symptoms, or the infection may be entirely asymptomatic (without symptoms).

The reason that EBV is so mild in babies and younger children is poorly understood. Some experts theorize that a type of immune cell called natural killer (NK) cells—which are at highest at birth—might afford children special protection.

Others contend that symptoms are more severe in teens and young adults because they pass larger amounts of the virus—which is transmitted in saliva—through kissing.

It is also possible that some people infected as children may have an exaggerated immune response when re-exposed to the virus. In such cases, the body will have developed an immune defense during the initial, asymptomatic infection and may overreact when re-exposed to EBV as a teen or young adult.

Irrespective of the cause, EBV infections in children usually cause no symptoms or only mild symptoms that are indistinguishable from other brief childhood illnesses.

Older Adults (40 and Older)

Mononucleosis in older adults is rare and more often associated with a weakened immune system. Older adults often develop a fever lasting longer than two weeks but may not have other classic signs or symptoms. If they do, they tend to be mild and easily dismissed or ignored.

Despite the lack of classic symptoms, older adults with mono are vulnerable to potentially serious complications affecting the spleen, brain, blood, and liver.

This may be explained in part by the fact that around 95% of the world's population is infected with EBV. Of these, around 50% are infected by age 5, and 90% are infected by age 30. That leaves a very small proportion of the population uninfected after age 40.

Because older adults generally have weaker immune systems, they may be able to temper the initial infection but not control it. In some people, this can lead to disease progression and complications like severe anemia and liver inflammation.

Complications

Complications of mononucleosis are uncommon but can be serious. The risk is greater the older a person gets.

Possible complications include:

  • Rash: EBV can cause a widespread, measles-like rash if it is inappropriately treated with antibiotics.
  • Hemolytic anemia: This type of anemia is caused when red blood cells are destroyed faster than they are made. EBV can suppress bone marrow which produces red blood cells. Splenomegaly can also cause red blood cells to be removed from the bloodstream sooner than normal.
  • Hepatomegaly: This is the enlargement of the liver, mainly seen in older adults with mono. When severe, hepatomegaly can lead to non-viral hepatitis and symptoms like severe fatigue, loss of appetite, dark urine, clay-colored stools, and jaundice (yellowing of the skin and eyes)
  • Ruptured spleen: On rare occasions, splenomegaly can cause the spleen to rupture, leading to massive, often life-threatening internal bleeding.
  • Nervous system complications: Mono can affect the nervous system, causing meningitis (swelling of tissues around the brain and spinal cord), encephalitis (swelling of the brain), Guillain-Barré syndrome (an immune system disease), and facial palsy (facial paralysis).
  • Myocarditis: This is inflammation of the heart muscle, which can lead to chest pain, irregular heartbeats, shortness of breath, and complications like heart failure, heart attack, and stroke.

Can Mono Get Into Your Lungs?

It is rare for mononucleosis to affect the lungs, but there have been rare instances when EBV has disseminated (spread) into the bloodstream and caused inflammation of the lungs, known as pneumonitis.

While few cases have been reported in the medical literature. EBV pneumonitis can be especially severe and mostly involves people who are severely immunocompromised.

Relieving Symptoms of Mononucleosis

As debilitating as it can be, mononucleosis is usually a self-limiting condition—meaning it will run its course and go away on its own. Treatment is mainly focused on the management of symptoms.

In addition to prolonged rest, a healthcare provider may prescribe:

  • Saltwater gargles: These can help soothe a sore throat and reduce bacteria that can lead to a secondary infection.
  • Over-the-counter pain relievers: These include Tylenol (acetaminophen) and nonsteroidal anti-inflammatory drugs (NSAIDs) like Advil (ibuprofen). NSAIDs are intended for occasional relief as their overuse can lead to gastric bleeding and ulcers.
  • Ice application: A cold compress on the forehead can help bring down a fever as can a cooling bath or a cold foot bath.
  • Prednisone: This is a prescription oral steroid that may be used to treat severe tonsillitis (although the use of the drug remains controversial).

Antiviral drugs are not recommended for people with simple cases of mononucleosis but may be used to treat EBV complications like hepatomegaly, encephalitis, or hemolytic anemia.

Antibiotics are not used because they treat bacterial infections, not viral ones. The only exception is if there is a secondary infection like tonsillitis.

When to See a Healthcare Provider

You should see the healthcare provider when you have the symptoms of mononucleosis. This is because EBV infection can mimic many other diseases, including cytomegalovirus (CMV), HIV, rubella, hepatitis A, Lyme disease, and toxoplasmosis, among others.

Some of these "copycats" require immediate medical treatment and can lead to severe complications if they aren't addressed.

Arguably, the greatest concern related to mononucleosis is splenomegaly. Although the rupture of the spleen is rare, healthcare providers will often recommend that you take it easy during recovery and activities or sports that can cause an accidental rupture.

When to Call 911

A ruptured spleen is a medical emergency. If you have mononucleosis, call 911 or seek immediate emergency care if you develop symptoms like:

  • Pain across the abdomen
  • Tenderness in the upper left abdomen
  • Dizziness or lightheadedness
  • Pain that radiates to the left shoulder
  • Blurred vision
  • Rapid heartbeats
  • Abnormally pale skin
  • Confusion or changes in your mental state

Mononucleosis Doctor Discussion Guide

Get our printable guide for your next healthcare provider's appointment to help you ask the right questions.

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Summary

Symptoms of mononucleosis include a sore throat, fatigue, malaise, swollen lymph nodes, mild fever, and swollen tonsils. Adolescents, teens, and young adults are more likely to be affected.

Babies and children are less commonly affected and may have few, if any, symptoms. Older adults often lack the "classic" symptoms of mononucleosis but are more susceptible to potentially severe complications like anemia, an enlarged liver, and a ruptured spleen.

10 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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Additional Reading

By Vincent Iannelli, MD
 Vincent Iannelli, MD, is a board-certified pediatrician and fellow of the American Academy of Pediatrics. Dr. Iannelli has cared for children for more than 20 years.