8 Signs You Could Have Mono–and You're Not Just Super Tired

The so-called kissing disease is known for causing extreme fatigue, but it's not the only mono symptom to watch for.

Jaundice mono enlarged liver hepatomegaly
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Mono, short for mononucleosis, is a common viral illness–and unwelcome rite of passage–for many adolescents and young adults. College students are particularly vulnerable, but infants and young children can get it too (although their mono symptoms are usually mild, if they have symptoms at all).

Classic signs of mono include fever, sore throat, swollen lymph nodes, and fatigue. Doctors often diagnose this infection based on a patient’s symptoms and physical exam results, although sometimes mono blood testing is ordered to confirm the diagnosis or rule out other causes.

Serious complications can occur, but most people recover with plenty of rest, fluids, gargling, and over-the-counter pain relievers. (Mono treatment is pretty much what your mom would recommend!)

Is mono contagious?Let’s put it this way: Mono is called “the kissing disease”–and not because there’s anything romantic about it! The Epstein-Barr virus (EBV), the most common cause of mono, hitches a ride in people’s saliva.

“You can pass it on when you have direct sharing of secretions, like kissing or sharing a cup,” says Christine Hermos, MD, assistant professor at the University of Massachusetts Medical School and pediatric infectious disease specialist at the UMass Memorial Children’s Medical Center.

Luckily, mono is less contagious than the common cold. People with mono don’t usually have coughing or sneezing, so they’re not spraying virus-containing droplets of saliva into the air, Dr. Hermos explains.

Mono can also be spread through blood and semen, but that occurs less frequently, according to the U.S. Centers for Disease Control and Prevention (CDC).

If you do come in contact with mono, it can take four to six weeks after you’ve been infected for mono symptoms to even appear. Many people start to feel better two to four weeks after that, but fatigue can persist for many weeks or even months.

So, how long are you contagious with mono? Studies have not established a firm timeline. It may depend on your symptoms, so patients should talk to their doctors. “I usually tell them they’re probably shedding virus for about three weeks until their fever resolves,” Dr. Hermos says.

At least it’s uncommon to get mono more than once. After you’ve had mono, the Epstein-Barr virus hides in your body but rarely causes symptoms a second time. Roughly 90% of adults have antibodies against Epstein-Barr in their blood, meaning they’ve been exposed to the virus years earlier, probably in childhood.

Think you might be tangling with a case of mono? Here’s a symptom-by-symptom checklist of what to look for.

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Sore throat

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People often confuse mono with strep throat, a painful bacterial infection of the throat.

With mono, your throat can be severely sore or itchy, and some people have difficulty swallowing, says Sherly Mathew, MD, an internal medicine physician with Health Quest Medical Practice in Hyde Park, New York.

It’s not uncommon to see white patches on patients’ tonsils, she notes. And, “sometimes you will see a little bit of rash inside the mouth on the upper palate.”

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Swollen lymph nodes

Lymph nodes play a role in cancer diagnoses, as well as trapping bacteria and viruses.

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Fever or chills

Woman with fever taking temperature with thermometer
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People with mono usually have a fever, ranging from 102 to 104 degrees, Dr. Mathew says.

A lot of patients say their fever peaks in the afternoon or evening, “and that could continue for a few days to weeks, depending on how they fight the infection,” she adds.

You can get chills too, as your body responds to the fever.

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Headache or muscle ache

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Mono can lead to any number of vague symptoms, like headaches or muscle pains, perhaps sparked by other discomfort.

“Anyone with fever and fatigue will have headache,” Dr. Mathew says.

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Skin rash

Skin rash mono antibiotics strep
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A pink or red splotchy or measles-esque skin rash is a less common sign of mono. It can occur as a reaction to antibiotics, Dr. Hermos says.

While antibiotics are not used to treat mono, “some people test positive for strep when they have the Epstein-Barr virus,” she explains. When they take antibiotics for the throat infection, they break out in a rash. “That’s another clue you could have EBV.”

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Swollen spleen or sore upper abdomen

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The spleen is a blood-filtering organ that plays a role in fighting infections. When you have mono, it can become inflamed.

You may feel some tenderness when your doctor presses on the upper left part of your abdomen.

You shouldn't participate in sports for three to four weeks after getting mono. Any trauma to the abdomen can cause your swollen spleen to rupture. If you have sudden, sharp abdominal pain, seek emergency medical treatment.

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Jaundice mono enlarged liver hepatomegaly
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People with mono can develop jaundice, a yellowing of the eyes or skin due to a problem with the liver. Dr. Hermos recalls having a few mono patients over the years whose parents noticed that the whites of their kids’ eyes were tinged with yellow.

Jaundice suggests that the liver is enlarged, a condition called hepatomegaly, which can be a complication of mono, Dr. Mathew explains.

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