What Is Mononucleosis (Mono)?

  • 1st Revision: Bea Brownlee


Infectious mononucleosis, also known as mononucleosis or just ‘mono,’ is a contagious disease. However, it is not considered highly contagious, as it is mainly spread through saliva. This is why it is often referred to as the ‘kissing disease.’1

Young adults and teenagers are the groups most commonly affected by mono. The illness is accompanied by symptomssuch as fever and swollen lymph nodes. Infectious mononucleosis usually goes away on its own, but there are several treatment options that you can use in the meantime to manage your symptoms. 

Causes of mononucleosis

The Epstein-Barr virus is the main cause of infectious mononucleosis.2 According to the CDC, the Epstein-Barr virus is also called human herpesvirus 4. Most people will contract this virus at some point in their lives. However, this does not always result in developing symptoms of mononucleosis.3

Mono isn’t called the ‘kissing disease’ for nothing. The main way that it spreads between people (mainly adolescents and young adults) is through kissing, as saliva is the main mode of transmission of the Epstein-Barr virus. Other ways to contract mono include:3

  • Sharing food and drink
  • Sharing personal items, such as toothbrushes or utensils
  • Coughing and sneezing

Less common ways to contract mono include:

  • Blood transfusions
  • Organ transplants

Children are not exempt from developing mononucleosis. However, the way children get infected by the Epstein-Barr virus is less well understood than adolescents, who contract it mainly through kissing. Currently, it is thought that children catch it from their parents or relatives who may be symptom-free carriers of the Epstein-Barr virus.4

Although the Epstein-Barr virus causes 90% of mono cases, there are other viruses and germs that less commonly cause the illness. These can include:

  • hepatitis A, B and C
  • adenovirus
  • rubella
  • HIV
  • cytomegalovirus
  • toxoplasma (a type of parasite, not a virus)2,3

The time it takes from initially coming into contact with the viruses to developing infectious mononucleosis symptoms is between 3-6 weeks.4 

Signs and symptoms of mononucleosis

Not everyone who catches the Epstein-Barr virus develops mononucleosis. However, those who do develop symptoms tend to have a sore throat first. Patients usually describe this as being the worst sore throat they have ever had. 

The other two most common symptoms of mono are a fever and swollen lymph nodes. 

Other symptoms may include:

  • headache
  • enlarged spleen (which causes pain in your upper left abdomen)
  • rash
  • fatigue (extreme tiredness)
  • general feeling of being unwell
  • loss of appetite
  • muscle weakness and aching

Symptoms usually resolve within approximately 2 weeks. However, fatigue may continue for a few months after the illness has gone. 

It is important to note that sometimes people who have infectious mononucleosis are asymptomatic, meaning that they have the illness without any symptoms. This is true for about 15% of people who have mono.4 

Most people only develop mono once, but the Epstein-Barr virus remains dormant in your body forever after your symptoms have resolved. If your immune system is weakened, perhaps due to having another illness, the virus can reactivate and you may develop mononucleosis more than once.3


Although not many people who have mono go on to develop complications, they are still worth discussing as they can be serious. According to Mayo Clinic, these complications include:

  • nervous system complications (such as meningitis and Guillain-Barre syndrome)
  • myocarditis (heart muscle inflammation)
  • hepatitis (liver inflammation)
  • ruptured (burst) spleen
  • anaemia (reduced red blood cells)

Management and treatment for mononucleosis

There is no vaccine or cure for mono, and antivirals that work for other viral illnesses have no effect on the Epstein-Barr virus. 

However, your healthcare provider may prescribe medication to help ease some of your symptoms. This could include anti-inflammatory painkillers like ibuprofen to help get rid of your fever, fatigue or sore throat.3 

The main focus of treatment when it comes to mono is managing and relieving your symptoms. To do this, the following is recommended:

  • Rest: this will provide your body with enough energy to fight the infection, and may also help with fatigue
  • Stay hydrated: mono symptoms like fever and loss of appetite can cause dehydration
  • Take painkillers: these may help relieve your headache, fever, sore throat and muscle weakness/aches
  • Avoid sports: playing sport is not advised within the first 3 weeks of developing mono. 50% of people who develop infectious mononucleosis symptoms have an enlarged spleen.2 Physical activity puts pressure on it and increases the risk of it rupturing. 

Serious complications usually only develop after 1% of infectious mononucleosis cases, but they can still occur.4 In this instance, treatment will be focused on managing the complications. 


How is mononucleosis diagnosed?

To diagnose mono, your healthcare provider will start by asking about any symptoms that you have been experiencing. They will also check for any swelling of your lymph nodes and signs of an enlarged spleen or liver.

A blood sample is used for the infectious mononucleosis diagnostic test of choice - the heterophile antibody test - to check if your immune system has made antibodies that fight the Epstein-Barr virus. Blood tests can also find out if you have an increased white blood cell count, which indicates that your body is fighting an illness.3 

How can I prevent mononucleosis?

With there being no vaccine for mononucleosis, the best ways to prevent the illness are avoiding people with symptoms and practising good hygiene. Good hygiene will either prevent the Epstein-Barr virus from entering your system, or alternatively, it will prevent you spreading the virus to other people.

To practise good hygiene:

  • don’t share food and drinks with other people
  • don’t share personal items such as toothbrushes
  • wash your hands regularly
  • cover your mouth when you cough or sneeze

Who is at risk of mononucleosis?

Teenagers and young adults are more likely to get mononucleosis. With that being said, it is possible for anyone to contract mono. Your risk of contracting mono is increased if you have a weakened immune system.

How common is mononucleosis?

Infectious mononucleosis is very common. About 90% of adults worldwide test positive for the Epstein-Barr virus.2 However as mentioned previously, it is possible to have the virus and not develop mono, especially if you have had mono before. In fact, according to the Cleveland Clinic, only about 25% of people with the Epstein-Barr virus develop mono.3 However, bear in mind that it can also be caused by other viruses.

The highest incidence of mono is usually in the 15-24 year old age group. Mononucleosis only accounts for about 2% of pharyngeal diseases (diseases of the throat) found in adults.

When should I see a doctor?

You should contact your doctor or healthcare provider if you experience any of the following symptoms, as they could indicate something more serious:

  • struggling to breathe
  • dizziness
  • severe muscle weakness
  • severe headaches

As many patients with mono have an enlarged spleen, you should also be aware of the symptoms of a ruptured spleen. If you notice any of the following symptoms, seek medical attention as soon as possible:

  • asharp pain in the upper left part of your abdomen
  • lightheadedness
  • confusion
  • blurred vision
  • fainting2


Infectious mononucleosis, also known as ‘mono’ or the ‘kissing disease,’ is an illness caused mainly by the Epstein-Barr virus. It is transmitted mainly through saliva, and is more common in the adolescent and young adult age groups. Symptoms include a sore throat and swollen lymph nodes. The best way to prevent mono is by practising good hygiene and avoiding contact with those who have it. Symptoms usually go away on their own, but your healthcare provider can prescribe medication to help ease the symptoms. 


  1. Mononucleosis (Mono) [Internet]. familydoctor.org. 2017 [cited 2023 Mar 10]. Available from: https://familydoctor.org/condition/mononucleosis/?adfree=true
  2. Mohseni M, Boniface MP, Graham C. Mononucleosis. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 [cited 2023 Mar 10]. Available from: http://www.ncbi.nlm.nih.gov/books/NBK470387/ 
  3. Mononucleosis (Mono) [Internet]. Cleveland Clinic. 2015 [cited 2023 Mar 10]. Available from: https://my.clevelandclinic.org/health/diseases/13974-mononucleosis
  4. Dunmire SK, Hogquist KA, Balfour HH. Infectious Mononucleosis. Current Topics in Microbiology and Immunology [Internet]. 2015 [cited 2023 Mar 10];390(2):211–40. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4670567/
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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