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Infectious Mononucleosis 101: Everything You Need to Know

When it comes to an infectious disease like mononucleosis, you’re sure to have lots of questions. How do you get mono? Is it contagious? What are the symptoms of mono in adults? Here, we’re going to answer those questions and more.

Various medicines, a thermometer, sore throat sprays

What is mono? 

Infectious mononucleosis is an acute condition caused by the Epstein-Barr virus (EBV) or human herpesvirus type 4. Though the mono virus is usually passed on through saliva, it can also be transmitted through respiratory secretions (like sneeze and cough), or by sharing a glass or silverware with someone who’s infected. While the mono disease is considered ‘infectious’ since it can be passed from person to person, it’s less so than some other illnesses, including the common cold.

The groups most vulnerable to getting mono are teenagers and young adults ages 15 to 25. In fact, the Centers for Disease Control and Prevention report that one in every four teenagers or young adults who get the EBV infection will develop infectious mononucleosis. It’s pretty common. 

With that said, it can also affect other age groups, including young children. Children tend to not to show many symptoms, which means the infection sometimes goes unnoticed. A child who gets EBV will be immune to the mono disease for the rest of his or her life. 

Mono symptoms 

So, how can you tell if you have mono? The symptoms of mono in adults usually start to appear about four to seven weeks after you get the virus. The incubation period is around 4-8 weeks and may be shorter in young children. Some of the early mono symptoms include:  

Throat specialist examining lymph nodes of his patient with mono symptoms

After a day or two, you might also experience the following mono symptoms:

  • Swollen lymph nodes in your neck and armpits
  • Hepatosplenomegaly
  • Bruise-like areas inside the mouth (palatal petechiae)
  • Soreness in the upper-left abdomen
  • Tonsillitis 

Schedule a visit with your doctor if you notice any of the following:

  • The symptoms of the mono disease last longer than 10 days
  • You have a serious sore throat for more than 2 days
  • You get swollen lymph nodes all over your body
  • The abdominal pain gets severe
  • You have a terrible headache and a stiff neck

How do you get mono? 

Infectious mononucleosis is usually a result of the Epstein-Barr virus (EBV), but other viruses can cause it, too. EBV belongs to the herpes virus family and it's fairly common — the majority of people will be infected with the virus at some point in their lives. It’s also possible to be infected with the virus and be a carrier throughout your life, without ever experiencing the symptoms of mono.

Epstein-Barr virus which causes infectious mononucleosis

EBV spreads through bodily fluids, which means you can get it through:

  • Contact with the saliva of an infected person (hence the nickname ‘the kissing disease’)
  • Sharing food, drinks, or silverware with someone who’s infected
  • An infected person sneezing or coughing near you

Although it’s less likely, the mono virus can also spread through blood and blood transfusions, semen, organ transplants, and sexual contact.

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Mono complications

While it generally resolves itself within two to four weeks, the mono virus can lead to complications that can turn into serious problems. This is particularly a concern for people with already-weakened immune systems. Some of the complications that can arise from mono include:

  • Enlarged spleen: The mono virus can cause swelling in the spleen, which can increase the risk of the organ rupturing. A splenic rupture is a life-threatening condition.
  • Liver inflammation: The mono disease can also lead to mild liver inflammation (hepatitis) and a yellowing of the skin and the eye whites, which is called jaundice. 
  • Respiratory problems: This can include upper airway obstruction.
  • Anemia: The mono virus can lead to a decrease in red blood cells and hemoglobin — this is called hemolytic anemia (usually treated with rituximab).
  • Thrombocytopenia: This means that you have low levels of platelets in your blood, which can affect the body’s ability to form clots
  • Heart problems: While uncommon, mono can cause inflammation of the heart muscle, called myocarditis.
  • Nervous system complications: Problems that can arise from mono include meningitis, encephalitis, and Guillain-Barre syndrome, though they are rare.
  • Swollen tonsils: This can result in difficulty breathing.

Mono diagnosis and treatment

Diagnosing the mono virus is usually done with the help of blood tests and a physical examination by a doctor. Although it’s the Epstein-Barr virus that causes mono, your doctor will likely want to check for strep throat and other conditions, as well. 

Here’s what you can expect through the diagnosis process:

  • A physical evaluation where the doctor examines your throat checks your neck for swollen lymph nodes and listens to your lungs. 
  • A complete blood count to check for mono disease, which may show an increase in lymphocytes, the presence of atypical lymphocytes and low platelet count.
  • A rapid strep test, particularly if you have a sore throat. This will rule out strep throat.
  • A monospot test to check for the mono virus. It detects heterophile antibodies using RBCs from horses. The specificity of monospot test is around 100% and its sensitivity is around 85%.
  • An antibody test if your monospot test comes back negative. This test looks for EBV antibodies. 

Mono prevention 

Unfortunately, there’s no vaccine that can prevent infectious mononucleosis. Mono’s incidence is about 500 cases in 1,000,000 per 1 year in the US. Healthy people can carry the mono virus and pass it on to others for the rest of their lives. The good news is that you usually only get mono once, and by the age of 35, your body will have built up antibodies to fight the disease.

Typically, the mono virus isn’t serious and goes away on its own in a month or two. To help your recovery along, make sure you get plenty of rest, drink lots of water, eat a nutritious diet, and take an over-the-counter pain reliever if you need it. Avoid physical activity that may trigger splenic rupture (like contact sports) for at least 3 weeks after the onset of symptoms. It’s important to be patient with your body as it fights the infection.







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