Mono Symptoms in Kids: Signs, Diagnosis, Treatment

Although many kids don't show symptoms, it is very contagious

Mono symptoms in kids include flu-like symptoms, fever, and swollen lymph nodes. However, many kids show no symptoms of mono.

Infectious mononucleosis (also called "mono"), is a viral illness that is very contagious. It is common in teenagers and college students. Kids can easily get mono if they share a water bottle with a sick friend or are kissed by a family member with the infection.

Mono is spread by saliva and other bodily fluids such as blood and semen. It is usually caused by the Epstein-Barr virus (EBV) and sometimes the cytomegalovirus (CMV). Once your child recovers from mono, the virus stays dormant in their body.

While many of the symptoms are similar to mono in adults, the virus can present differently in children. 

This article will go over mono symptoms in kids. You'll also learn how mono is diagnosed in kids, how children are treated for mono, and tips for preventing mono.

Teenage girl sick in bed

Justin Paget / Getty Images

Frequent Symptoms of Mono in Kids

It’s common to mistake your child’s mono symptoms for the flu or strep throat. Since mononucleosis is usually associated with teens and college kids, you may not think that a child can get mono.

When a child is infected with mono, they won't have symptoms right away. It usually takes a month or two for the symptoms of mono to start.

Once they show up, mono symptoms can last several weeks. If your child does not show any improvement after a few days, talk with your healthcare provider about a possible mono diagnosis. 

While each case of mono is unique, some of the most common symptoms include:

  • Swollen lymph nodes: Swollen lymph nodes are a common symptom of mono and occur in almost 90% of cases. When your child’s lymph nodes are swollen, it means their immune system is fighting off an infection. 
  • Fever: A mild to moderate fever is another common mono symptom. Your healthcare provider will most likely recommend giving your child acetaminophen or ibuprofen to manage the fever and discomfort. 
  • Fatigue: While most mono symptoms last two to four weeks, the fatigue can linger for weeks to months. If your child is so tired that they no longer want to get out of bed or eat meals, talk with your practitioner.
  • Sore throat: Most children with mono report a sore throat. This may be due to swelling of the lymph nodes and tonsils, making swallowing painful. 
  • Body aches: It’s common for children and teens to experience muscle aches with mono. Encourage rest, liquids, and pain medicine if needed. 
  • Loss of appetite: Many children lose their appetite when they are ill with mono. This could be due to fatigue or painful swallowing. Encourage your child to drink as much fluid as possible to prevent dehydration.
  • Enlarged spleen: It’s common for children and teens with mono to have an enlarged spleen during the illness. When the spleen is enlarged, it may start to filter out normal red blood cells and platelets, leading to their low levels in the blood. In most cases, the spleen returns to its normal size on its own.
  • Swollen liver: It’s possible for children with mono to have a mildly inflamed liver. This usually resolves on its own once they start feeling better. If you notice a yellowing of your child’s eyes or skin, known as jaundice, call your healthcare provider. 

How Long Is Mono Contagious in Kids?

A child with mono can spread the infection to others for as long as they are having symptoms. That means they could be contagious for weeks if not months.

They might also be able to keep spreading the virus after they get better, but studies haven't found a definitive answer for how long mono remains contagious once a person heals.

It's also possible for people to be carriers of mono. This means that they get infected and can spread the virus to other people without ever feeling sick themselves.

Rare Symptoms of Mono in Kids

Mono can be serious in children. Most people are familiar with the common symptoms of mono like fatigue and fever, but you may not be aware of these rare symptoms:

  • Anemia: Mild anemia can occur when your child has mono, but it generally improves on its own within one to two months. This is usually the result of an inflamed spleen.
  • Thrombocytopenia: It’s possible for your child to experience a low platelet count during a mono illness. Platelets are the cells responsible for clotting your blood. This also usually resolves on its own. 
  • Difficulty breathing: You may notice that your child’s tonsils appear swollen. This is normal during mono. In rare cases, the tonsils can become so swollen that they begin to block your child’s airway. Any difficulty breathing requires emergency treatment. 

How Mono in Kids is Diagnosed

Diagnosing mono in children is the same as diagnosing it in older teens and adults. Your child's provider will ask you about their symptoms, do an exam, and may order some blood tests.

Here's what your child's provider will check for to diagnose mono:

  • Swollen tonsils and/or lymph nodes
  • An enlarged liver and/or spleen
  • A "monospot" test to look for antibodies to the virus
  • Signs of infection on a blood test (such as a high white blood cell count)

Mono Treatment for Kids

Kids with mono get the same treatment as teens and adults. They need to focus on resting and staying hydrated and nourished.

Since mono is caused by a virus, antibiotics won't help your child get better. That said, over-the-counter pain and fever medicine like ibuprofen might help with their symptoms.

A child with mono may need to take it easy for several weeks or even a month. Their provider might also put limits on how active they can be while they're sick, especially if their spleen is enlarged.

Complications of Mono in Kids

Mono can lead to other, more serious health conditions. The complications of mono in kids include:

  • Ruptured spleen: When your child’s spleen is enlarged due to mono, they are more at risk of experiencing a ruptured spleen. This is a serious complication and requires emergency surgery. To help avoid a spleen rupture, your pediatrician will recommend no contact sports or heavy lifting for at least four weeks. 
  • Guillain-Barre syndrome: This autoimmune syndrome is a rare complication of mono that occurs when a child’s peripheral nerves are damaged by the virus. When the nerve endings are damaged, they cannot transmit signals normally, and this results in temporary paralysis. 
  • Meningitis: Meningitis occurs when the membranes and fluid that surround the brain and spinal cord are inflamed. This inflammation can be triggered by a viral infection like an EBV infection. 
  • Encephalitis: Inflammation of the brain is known as encephalitis. It can manifest as behavioral changes, seizures, and loss of consciousness. 
  • Myocarditis: Myocarditis refers to inflammation of the heart muscle. This is a rare complication of mono; symptoms include chest pain and shortness of breath. 
  • Reye’s syndrome: This syndrome can occur as a result of aspirin use in children. To lower the risk of Reye’s syndrome, talk with your practitioner about safe analgesics for your child, like acetaminophen or ibuprofen. 
  • Hemophagocytic syndrome: This rare condition can be caused by EBV and causes a child’s white blood cells to attack their other cells. This process leads to an enlarged spleen and liver, as well as nervous system problems.  

When to See a Healthcare Provider or Go to the Hospital

If your child has mono symptoms, like a fever, swollen lymph nodes, and fatigue, they'll need to get medical care. Remember that mono symptoms usually last longer than those of a cold or the flu. If your child is not starting to feel better a few days after symptom onset, call your pediatrician. Your provider's office staff will help you determine if you should bring your child into the clinic or opt for a telehealth visit. 

Your pediatrician will start by asking about your child's symptoms and will then perform a physical exam to look for signs of infection. They may also ask you to go to the lab for blood tests, such as a white blood cell count or monospot test, to confirm the diagnosis.

Even after your child has been diagnosed with mono, don’t hesitate to call your provider if their symptoms change or if you are concerned.  Any sign of a serious complication such as difficulty breathing, confusion, or paralysis needs to be evaluated immediately.

Preventing Mono in Kids

Your child can't get vaccinated against mono like they could the flu. That said, you can protect your child from mono by practicing many of the habits that prevent other infectious illnesses, like colds and COVID-19.

Here are a few steps you can take to prevent mono:

  • Teach your child how to wash their hands properly and make sure they wash their hands frequently—especially before they eat and after they use the bathroom.
  • Tell your child not to share cups, water bottles, utensils, toothbrushes, or any other item they would put in their mouth with other people (e.g., classmates, friends, family members).
  • Keep your child away from people who are sick as much as possible. If someone in your family gets mono, try to keep your child separated from them. At the very least, make sure they don't hug and kiss the person until they are well. If everyone is in close quarters, wearing face masks can be helpful.
  • Make sure that the surfaces and objects for eating are clean. Wash them with hot water and soap, run them through the dishwasher, or boil them. If your child or another member of your family is sick, you can also have them use disposable utensils and dishes until they're better.
  • Launder bedding and clothes in hot water, especially after someone has been sick.

Summary

Mononucleosis or "mono" is a common viral infection. It's usually associated with teens and college kids, but children can get mono too. At first, the symptoms of mono in kids can seem like a cold or the flu. However, they tend to last several weeks. There's no specific medicine to treat mono in kids—mostly, they'll just need to rest.

A Word From Verywell

The long list of potential symptoms and complications of mono can be overwhelming for any parent. It’s helpful to remember that most children and teens who are diagnosed with mono experience swollen lymph nodes, fever, and fatigue, and these symptoms usually resolve on their own. Talk with your healthcare provider if you suspect that your child has become ill with mono, and stay in close contact with them if your child’s symptoms start to change. 

Frequently Asked Questions

  • How does a kid get mono?

    Mono is spread through body fluids. It's easy for kids to pick up mono if they're exposed to the saliva of someone who is sick. For example, a child could get mono from sharing a water bottle with a sick friend or kissing a family member with the virus.

  • How serious is mono in a child?

    Kids with mono usually get better in a few weeks as long as they rest and follow their pediatrician's recommendations about activity—for example, not playing sports until they are healed.

    In some cases, mono can lead to more serious health problems. One of the most serious complications of mono is a ruptured spleen. If your child has mono and has an enlarged spleen, making sure they are not doing too much activity is important to protecting their spleen.

    It's not common, but some children with mono may develop other conditions, like brain swelling (encephalitis), Guillain-Barre syndrome, or inflammation in their heart (myocarditis).

  • How long is mono contagious?

    A child with mono is contagious for as long as they have symptoms. This could be anywhere from a couple of weeks to a month.

    It's also possible for people to be carriers of mono but not get sick. This means they can pass the infection to other people without ever having symptoms of mono themselves.

  • How long does mono last in a child?

    Children with mono won't start feeling sick for a month or even two months after they've caught the virus. Once they start feeling unwell, the symptoms of mono can last anywhere from two weeks to over a month.

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