Are Mono Symptoms Contagious?

What is mono?

Mono symptoms like fever, swollen glands, sore throat, and fatigue may be contagious for up to 18 months.
Mono symptoms like fever, swollen glands, sore throat, and fatigue may be contagious for up to 18 months.

Mono is short for mononucleosis, a viral disease most commonly caused by an infection of the Epstein-Barr virus (EBV). Once a person has EBV, the virus begins to shed in the throat and is known to cause symptoms like fever, swollen glands, sore throat, and fatigue.

Doctors are unsure about how long a person remains contagious with mono -- some studies suggest people can pass on the virus from immediate infection all the way up to 18 months later. Symptoms sometimes take a few days to weeks to show up. It's therefore difficult to determine the exact cause and timing of infection.

Symptoms of mono

Mono symptoms that are contagious usually appear four to six weeks after someone’s been infected with EBV. They can develop slowly, or not at all. The symptoms include:

Symptoms affect people differently. In some cases, the symptoms are mild, while in other cases, they can be so severe that people are unable to function normally and need medical assistance.

Symptoms can last from a couple of days to a couple of weeks. While rare, some people have developed what is known as “chronic” or “recurrent” mono, where they experience mono symptoms from time to time their whole lives. For the vast majority, however, recovery is usually total.

Teenagers and young adults are the most likely to contract mono, though you can get it at any age.

Causes of mono

Mono is spread from person to person primarily through infected saliva or other body fluids. Mono is also known as the “kissing disease” because people catch it from kissing an infected person and swapping saliva. However, the disease can be spread if someone comes in contact with infected saliva outside of the mouth, like on a toothbrush, drinking straw, or shared eating utensil.

Saliva is not the only way mono can spread. Transmission through blood or semen during sexual contact, blood transfusions, and organ transplantations have also been known to infect someone with EBV and subsequently, mono.

When to see a doctor for mono

You should consult a doctor if you experience any of the symptoms above for more than a day or two. After a physical exam, they will make an assessment if you have mono, or if more tests are needed.

Diagnosis of mono

Doctors can usually diagnose infectious mononucleosis based on symptoms. If they are unsure, however, specific laboratory tests like a blood test may be needed to identify the cause of illness in people who do not have a typical case of mono.

A simple blood test that can be done on-site is called a “mono spot” test. The test usually turns positive shortly after the onset of symptoms, but sometimes the test will remain negative for up to a week or longer, despite evident signs of illness.

The blood work of patients who have infectious mononucleosis due to EBV infection may show more white blood cells (lymphocytes) than normal, unusual looking white blood cells, fewer than normal blood platelets, and abnormal liver function.

Treatments for mono

There is no known cure or vaccine for mono. Usually, the disease runs its course and after a couple of weeks, symptoms go away and the person begins to feel better.


The most effective way to avoid contracting mono is to take safe and healthy precautions, such as avoiding kissing or sharing drinks, food, or personal items, like toothbrushes, with people who are or might be infected.

Symptoms can be relieved by drinking fluids to stay hydrated, getting plenty of rest, and taking over-the-counter medications like aspirin. You should not take penicillin antibiotics like ampicillin or amoxicillin, however, if you have mono.

You should also avoid most physical activity until fully recovered because mono causes the spleen to become enlarged. Strenuous activity like contact sports increases the risk of rupturing the spleen.


Bacterial Infections 101: Types, Symptoms, and Treatments See Slideshow
Centers for Disease Control and Prevention: "About Infectious Mononucleosis."

Cornell Health: "Mononucleosis."

Johns Hopkins Medicine: "How Long Is Mono Contagious."