What Is Mononucleosis? Symptoms, Causes, Diagnosis, Treatment, and Prevention

Mononucleosis (commonly known as mono or the “kissing disease”) is an illness that may be more prevalent than most people realize. It’s usually caused by the extremely widespread Epstein-Barr virus (EBV). (1,2)

In most cases, people recover from a bout of mono without any long-term effects. Usually medications will not help speed recovery, though some painkillers may ease symptoms. Knowing what precautions to take during the healing process can go a long way in helping you feel better sooner and avoid complications. (3,4)

For teens and adults who get sick with mono, the illness can knock them off their feet. Symptoms such as extreme fatigue, fever, muscle aches, and sore throat can be so debilitating that most people won’t be able to maintain their normal routines for several weeks. (2,4,5,6, 7)

Typical symptoms of mono include:

• Severe fatigue
• Fever
• Muscle aches
• Sore throat
• Swollen lymph nodes
• Headache
• Loss of appetite
• Pink rash all over the body that resembles measles
• Enlarged spleen or liver

Young children, however, are more likely to experience much milder symptoms, such as a mild fever, a temporary loss of appetite, or feeling more tired than usual. Or they may not have any symptoms at all. (5,6,7,8)

Doctors are not sure why teens and adults are hit harder by mono than younger children, but some believe that it may have to do with the differences in their immune systems, says Hank Balfour, Jr., MD, a professor at the University of Minnesota Medical School in Minneapolis. Dr. Balfour believes that the milder reaction to EBV may have something to do with the fact that young children have immune systems that are more “naive,” he says. “When you reach adulthood without having had that infection, you’ll be hit harder.”

Because so many symptoms of mono — fatigue, sore throat, and muscle aches, among others — are common to other infections, such as the flu or strep throat, it can be easy to mistake infectious mononucleosis for something else.

“Other things that can mimic mono include cytomegalovirus, toxoplasmosis, strep throat, and HIV,” says Eric Johannsen, MD, an associate professor at the University of Wisconsin School of Medicine and Public Health in Madison.

But if you have a sore throat and a fever for seven days or feel excessively exhausted, it may be a sign that you have mono, especially if you are a teen or young adult who has never had the illness before.

Mono is a contagious illness that’s caused primarily by EBV. (1,5) EBV is spread from one person to another through saliva, which is why mono is referred to as the “kissing disease.” It’s spread most efficiently through direct contact, but doctors also advise against sharing cups, utensils, or toothbrushes with anyone who has mono to avoid catching the virus that causes it. (2,3)

The virus can also be transmitted through sexual contact or, rarely, through blood transfusions. (2,6)

It’s not known exactly how long someone can be contagious after they get the virus. (9)

Doctors generally recommend that intimate partners and family members try to avoid contact with the saliva of someone who’s had mono for a few months after mono symptoms go away (including avoiding kissing and having sex). EBV can remain in the saliva for months, long after the usual four to six weeks that symptoms tend to linger. The exact length of time that someone with EBV is contagious can vary, however. (9)

“People can shed the virus in their oral secretions for several years, and the shedding is intermittent,” says Balfour. “Most people get the virus from someone who’s completely asymptomatic.” (1,2)

But that’s no reason to panic and avoid contact with anyone and everyone.

An estimated 90 to 95 percent of adults worldwide are infected with EBV — or have been at some point in their lives. (1,5,6) But not everyone who gets EBV will develop symptoms. Only 1 in 4 people who are infected with the virus go on to develop mono. (7)

Once you get EBV, the virus stays in your body for the rest of your life, though in most cases, it will remain harmless (and dormant, thanks to your immune system). Patients with AIDS and others with weak immune systems are at risk of reactivation of EBV and mono symptoms. Rarely, some patients will have a recurrence of mono symptoms months or years later. (10)

Infrequently, some people may go on to develop complications related to acute EBV infection and mono, such as anemia, hepatitis, immune disorders (such as MS), or nervous system problems (such as Guillain-Barré syndrome, meningitis, or Bell’s palsy). (2,7)

Although EBV causes an estimated 90 percent of mono, the illness can also develop as a result of these other infections: (7,11)

• Adenovirus
• Cytomegalovirus
• Hepatitis A, B, or C
• Herpes simplex virus
• HIV
• Rubella
• Toxoplasmosis

Learn More About EBV and Other Viruses That Cause Mono

In most cases, doctors are able to diagnose mono based upon a medical history and physical examination. Your doctor will check for swelling in the lymph nodes in your neck and armpits, as well as look for other signs of mono, such as tonsils that are inflamed, fever, a swollen liver or spleen, and possibly a pink measles-like rash on your body. They will also likely ask if you’re experiencing severe fatigue, sore throat, muscle aches, or other symptoms. (2,7)

If your doctor determines that your symptoms are not typical of mono or decides that more information is needed to make a diagnosis, they may turn to lab tests to rule out other infections or illnesses, including:

• Monospot Test The monospot test is also called the heterophile test. It is a blood test that checks for antibodies (proteins that form to attack foreign virus or bacteria cells) to EBV. It’s fast, inexpensive, and easy, but it may not detect EBV until the second week of infection and has been shown to produce both false positive and false negative results. (3,5,12,13,14)
• EBV-Specific Antibody Test Typically done when your doctor suspects mono but a monospot test comes back negative, this test can help show whether you have been infected with EBV and if the infection happened recently. (3,13,14)
• Blood Tests These look for elevated levels of lymphocytes (white blood cells), which can indicate infection. (7,3,13)

Prognosis for Mononucleosis

While the symptoms of mono can be severe enough to temporarily disrupt your daily routines, the good news is that they gradually improve with rest, plenty of fluids, and other at-home remedies to help you feel better. (2,16)

Your fever should subside in about 10 days or so, and your swollen lymph nodes and spleen should return to normal in about a month. And while some symptoms, such as fatigue, may linger for two to three months, most people recover fully without any long-term problems. (2,16)

Many of your mono symptoms, such as a sore throat, muscle aches, and fever, should improve in a couple of weeks to a month, but fatigue and enlarged lymph nodes and spleen may take a bit longer to go away. (3,17)

There is no cure for mono, and doctors typically don’t prescribe medication, though sometimes an over-the-counter analgesic may be recommended to treat fever or muscle aches. The gold standard mono treatment is usually to stay home, drink plenty of fluids, and get plenty of rest, Dr. Johannsen says. “Most people get back to normal after about four weeks,” he says. (2,3,7,18)

If the tonsils become so swollen that you have trouble swallowing or breathing, your doctor may prescribe steroids, but only as a last resort, as those medications may actually interfere with healing. “Steroids typically reduce immune system function,” says Johannsen.

Doctors also advise people with mono to avoid any activities or sports that are strenuous or require contact, to avoid rupturing the spleen, which often becomes enlarged as a result of mono.

A ruptured spleen is a medical emergency that requires immediate treatment to avoid serious complications, including death. If you have a sharp pain in the upper left part of your abdomen while recovering from mono, seek medical attention immediately. “With mono, the liver or spleen can get very swollen,” says Octavio Ramilo, MD, the chief of infectious disease at Nationwide Children’s Hospital in Columbus, Ohio. “So you need to be cautious.” (1,2,3,5,7,8)

Other symptoms for which you should seek immediate medical attention: (2,11,19)

• Difficulty breathing
• Problems swallowing
• Not urinating enough
• Severe headache
• Persistent high fever
• Weakness in your arms or your legs
• Yellowish color in your eyes or your skin
• Stiffness in your neck

Learn More About How Doctors Diagnose and Treat Mono

Prevention of Mononucleosis

Since mono is transmitted from one person to another through saliva, the best method to prevent infection is to avoid activities such as kissing or sharing food or utensils with someone who has the illness until they have fully recovered. (3,20)

It’s important to remember that EBV may be present in someone who’s had mono for months after the infection, so even if many of their symptoms — such as fever or sore throat — have improved, they may still be infectious. (3,20)

While there is currently no vaccine available for mono, researchers at the University of Minnesota’s Mono Project, led by Balfour, are working on creating what may be the first vaccine to protect against EBV. (1,3)

With mono, one possible complication is a ruptured spleen, a life-threatening condition that requires emergency surgery. (18)

While the vast majority of people who become sick with mono recover fully in two to four weeks, a small subset of people can go on to develop complications related to the illness.

Once someone recovers from mono, the EBV virus usually stays dormant in the body and doesn’t cause any further problems. But in some cases, the virus may reactivate in people with weakened immune systems, which can cause symptoms to recur. (5,6,21)

Rare complications of acute or recurred mono include: (2)

• Anemia
• Hepatitis with jaundice
• Problems with the nervous system (such as encephalitis, loss of function in the nerves that control movement of the muscles in your face, psychosis, and Guillain-Barré syndrome)
• Swelling or inflammation in the testicles

Worldwide, EBV infection is extremely common, with as many as an estimated 90 percent of adults having been exposed to the virus before age 30. Most cases occur in teens and young adults. (6,17)

The same holds true for the United States. Mono is most common among teenagers and young adults. (7)

Studies have also linked EBV infection to the development of autoimmune diseases such as multiple sclerosis and lupus. EBV is known to be linked to certain cancers, such as Burkitt’s lymphoma, Hodgkin lymphoma, and nasopharyngeal carcinoma. (1,21,22,23)

RELATED: Everything You Need to Know About the Different Types of Lymphoma

Researchers continue to investigate links between EBV infection and the development of these illnesses, as well as what role genetics and the environment may play in the relationship and how to reduce such risks. (1,21)

In people getting bone marrow transplants, EBV is linked to a serious postoperative complication called post-transplant lymphoproliferative disease. (1) Some organ transplant recipients who are immunosuppressed are treated with antiviral medication to prevent reactivation of mono. (24)

American Academy of Family Physicians

This useful info sheet published by the American Academy of Family Physicians summarizes science-backed facts about mono, addressing common questions about who gets it, typical symptoms, and more.

Centers for Disease Control and Prevention (CDC)

How is mono transmitted, and what’s the best way to prevent and treat the infection? These and more key questions about mono are addressed on this page from the CDC.

Cleveland Clinic

From whether mono is considered a sexually transmitted infection to what people who get the infection can expect when they see their doctor for diagnosis and treatment, the Cleveland Clinic provides detailed and easy to understand information about this common illness.

Mayo Clinic

Mayo Clinic breaks down facts about mono into sections such as symptoms, diagnosis, and treatment. Navigate to other fact sheets from the Mayo Clinic about EBV and links to find Mayo Clinic healthcare providers.

MedlinePlus

MedlinePlus provides basic info and links to further resources about mono.

The Mono Project

Researchers working on the Mono Project at the University of Minnesota study EBV, the virus that causes mono. Here, they detail useful facts about mono and detail some of their groundbreaking research (including their search for a vaccine to protect against mono and the spread of EBV).