Infectious Mononucleosis
A viral infection causing fatigue, sore throat, and swollen glands
Quick Facts
- Type: Viral infection
- Usual cause: Epstein-Barr virus (EBV)
- Common ages: Teens and young adults
- Key caution: Avoid contact sports (spleen risk)
Overview
Infectious mononucleosis, often called mono, is a common infection usually caused by the Epstein-Barr virus (EBV). It spreads mainly through saliva, which is why it is sometimes called the "kissing disease," though it can also pass through sharing drinks, utensils, or close contact.
Mono is most common in teenagers and young adults. It typically causes profound tiredness, a sore throat, fever, and swollen lymph nodes. The illness can last several weeks, and the fatigue may linger longer. Most people recover fully with rest and supportive care, but the spleen can become enlarged, so certain precautions are important during recovery.
Symptoms
Symptoms usually appear several weeks after exposure and can develop gradually:
- Extreme fatigue and a general feeling of being unwell, which can be the most prominent symptom
- Sore throat, sometimes severe, that may be mistaken for strep throat
- Fever
- Swollen lymph nodes, especially in the neck and armpits
- Swollen tonsils, sometimes with a whitish coating
- Headache and body aches
- An enlarged spleen or a tender, swollen liver in some cases, occasionally with a rash
The intense tiredness can persist for weeks after other symptoms improve.
Causes
Most cases of infectious mononucleosis are caused by the Epstein-Barr virus, a member of the herpesvirus family. The virus spreads through saliva and other body fluids by:
- Kissing
- Sharing drinks, food, or utensils
- Coughing or sneezing
- Close personal contact
After infection, EBV stays in the body for life in an inactive form and can occasionally become active again, sometimes spreading to others even without symptoms. A few cases of mono are caused by other viruses.
Risk Factors
- Being a teenager or young adult
- Close contact with someone who has mono
- Sharing personal items such as cups and utensils
- Settings with close contact, such as schools and college campuses
Diagnosis
Doctors often suspect mono from the combination of fatigue, sore throat, fever, and swollen glands. Tests may include:
- Physical exam: Checking the throat, lymph nodes, and the abdomen for an enlarged spleen or liver.
- Blood tests: A monospot or specific EBV antibody test, and a complete blood count that may show characteristic changes in white blood cells.
- Throat swab: Sometimes done to rule out strep throat, which can occur at the same time.
Treatment
There is no specific cure; treatment focuses on relieving symptoms and allowing the body to recover.
- Rest: Plenty of rest, especially while fatigue is severe.
- Fluids: Drinking enough to stay hydrated, particularly with fever and a sore throat.
- Pain and fever relief: Over-the-counter medications to ease throat pain, headache, and fever, used as directed.
- Avoiding contact sports: For several weeks, because the enlarged spleen can rupture with a blow or strain.
- Caution with certain antibiotics: Some antibiotics can cause a rash in people with mono; antibiotics do not treat the virus itself.
Most symptoms ease within a few weeks, though tiredness can last longer.
Prevention
There is no vaccine for mono, but you can reduce spread:
- Avoid kissing or sharing drinks, food, utensils, or personal items with someone who has mono
- Wash your hands regularly
- Cover coughs and sneezes
- If you have mono, avoid sharing items and close contact until you feel better, to protect others
When to See a Doctor
See a doctor if you have a severe or persistent sore throat, high fever, or marked fatigue and swollen glands, especially in a teen or young adult, so the diagnosis can be confirmed and strep throat ruled out.
Seek emergency care for sudden, sharp pain in the upper left abdomen, which can signal a ruptured spleen, or for difficulty breathing or swallowing, severe weakness or dizziness, or a stiff neck with severe headache.
Frequently Asked Questions
How long does mono last?
The main symptoms, such as sore throat and fever, usually improve within two to four weeks, but fatigue can linger for several more weeks. Most people recover fully, though it is important to rest and avoid contact sports until your doctor says it is safe.
How does mono spread?
Mono spreads mainly through saliva, so it passes by kissing, sharing drinks, food, or utensils, and through coughs and sneezes. After infection, the Epstein-Barr virus stays in the body for life and can occasionally spread to others even when you feel well.
Why should I avoid contact sports with mono?
Mono can enlarge the spleen, and an enlarged spleen can rupture if struck or strained, causing dangerous internal bleeding. For this reason, doctors advise avoiding contact sports and heavy exertion for several weeks, until they confirm it is safe to return.
Can mono come back?
A repeat full-blown illness is uncommon because most people develop lasting immunity, but the Epstein-Barr virus remains in the body for life and can reactivate quietly. People with weakened immune systems may have more trouble with reactivation.
Do antibiotics treat mono?
No. Mono is caused by a virus, so antibiotics do not work against it. Antibiotics are only used if a separate bacterial infection, such as strep throat, is also present. Some antibiotics can even trigger a rash in people with mono, so they are used cautiously.
References
- Centers for Disease Control and Prevention (CDC). About Infectious Mononucleosis.
- Mayo Clinic. Mononucleosis — Symptoms and causes.
- MedlinePlus, U.S. National Library of Medicine. Infectious mononucleosis.
- American Academy of Family Physicians (AAFP). Infectious Mononucleosis.