11 Silent Signs of Mono You Shouldn’t Ignore

Updated: Feb. 24, 2021

The virus responsible for infectious mononucleosis (commonly known as mono) affects about 90 percent of the population worldwide, and most commonly strikes teenagers and young adults ages 15 to 30. Knowing what symptoms to look for can help catch the virus—and put you on the path to recovery—sooner.

Sore throat

If you have a sore throat, swollen tonsils, or swollen lymph nodes, especially on the sides of the neck, these could be mono symptoms. Talk to your doctor if you have this constellation of symptoms. He may decide to test for mono in addition to strep throat. “Many people have the Epstein-Barr virus (EBV)—the main viral cause of mononucleosis—in their system throughout their lives, but we can only tell through a blood test,” says Robert I. Danoff, DO, an osteopathic family medicine physician and program director of The Family Practice Residency and Family Medicine/Emergency Medicine Residency programs at Aria-Jefferson Health in Philadelphia. These sore throat home remedies work for people with mono or other sore throat causes.

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A rash

One of the first signs of mono is if you develop a rash after taking an antibiotic commonly used to treat a suspected strep throat, such as amoxicillin or ampicillin. “These antibiotics are used when a bacterial cause of a sore throat is suspected, prior to the healthcare provider knowing that mono is present. The rash is not an allergic reaction,” says Dr. Danoff.

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Someone you’ve kissed is sick

Mono is called the “kissing disease” because it’s easily and frequently spread through saliva (though it can also spread through blood or semen). While you can also pick it up by sharing cups or utensils, an easy clue that you might have more than a common cold is if you and someone you’ve intimately kissed have similar mono symptoms for a prolonged period of time. “It is difficult to prevent spreading mono because once a person has been infected with the EBV virus they can continue to shed it at various times throughout their life,” says Kim Alt, MD, a pediatric specialist at Rockford Pediatrics in Rockford, Michigan.

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Severe fatigue

Teens are notorious for being tired all the time, but if they feel severely exhausted for weeks on end (and exhibit other subtle mono symptoms), this could be one of the signs of mono. “Often the person says, ‘Doc, I’m sleeping a lot but I’m still tired and don’t feel like I’m doing too much,'” says Dr. Danoff. This might be a good time to test for the virus. Double-check that you’re not also guilty of these everyday things that could be making you tired.

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If you have a fever (usually greater than 100.4 degrees) or cold that sticks around longer than usual, it could be a sign of mono. “People should suspect mono when they have a prolonged cold-like illness or high fever and swollen glands. They should see their physician, who can confirm with a blood test,” says Adam Horblitt, MD, internal medicine physician at Westchester Medical Center in Valhalla, NY. Another common symptom is pharyngitis—a sore throat along with swollen tonsils.

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Difficulty breathing

“Complications of mono can cause obstruction of the airway from inflammation, causing difficulty breathing or wheezing,” says Dr. Horblitt. The majority of people who develop symptomatic mono recover within two weeks and develop a strong immunity to EBV, he adds.

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Abdominal pain

Pain or discomfort on the upper left side of the abdomen could signal an enlarged spleen due to EBV. Don’t play any rigorous contact sports, which could further damage the spleen, says Dr. Horblitt. In fact, avoid physical activity in general for about three weeks and talk to your doctor about when it’s safe to start up again. Mono is just one of the most common medical reasons for abdominal pain.

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Decreased appetite

If you don’t feel hungry or can’t bring yourself to eat despite abstaining all day, that could be one of the signs of mono, advises Dr. Horblitt. A healthy diet rich in fruits and veggies and plenty of fluids is key to recovering from the virus.

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Though less common and easier to attribute to something other than mono, a headache (accompanied by other mono symptoms) can be a sign of mononucleosis, says Dr. Alt.

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Poor hygiene

“Try not to touch your eyes, nose, or mouth; EBV can live on moist surfaces for hours and if you touch them and then your face, the virus has a pathway to get into your system,” says Dr. Danoff. Find out the other body parts that could make you sick if you touch them.

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Developing other illnesses

“Some rare but severe complications of mono include meningitis, encephalitis (inflammation of the brain), and Guillain-Barre (a paralysis disorder),” says Dr. Alt. Now that you know all about mono symptoms, find out how to avoid it with these tips from people who never get sick.