Infectious mononucleosis

Infectious mononucleosis, often called mono or glandular fever, is a viral condition. It is most often caused by the Epstein–Barr virus, or EBV.

EBV spreads mainly through saliva. This is why mono is sometimes called the “kissing disease,” although kissing is only one possible route. Sharing drinks, eating utensils, toothbrushes, or other objects exposed to saliva can also spread the virus.

Mono is especially noticeable in teenagers and young adults. Younger children often have few symptoms or symptoms that resemble a mild cold. Many people are infected with EBV at some point without ever being told that they have mono.

The condition matters because fatigue can be substantial and may continue after the fever and sore throat have improved. Mono can also enlarge the spleen, an organ under the left ribs that helps filter blood. An enlarged spleen is more vulnerable to injury, so temporary limits on exercise, heavy lifting, and contact sports are important.

Most people recover with rest and symptom relief. Antibiotics like amoxicillin or doxycycline do not treat mono because its usual cause is a virus, not bacteria.

Symptoms usually begin several weeks after exposure to EBV. They may develop gradually rather than all at once.

Common symptoms include:

• Marked tiredness or weakness
• Fever
• A painful or inflamed throat
• Swollen lymph nodes, especially at the back and sides of the neck
• Headache and body aches
• Reduced appetite

The tonsils may become enlarged and develop a white or yellow coating. This can resemble strep throat. Small red spots may appear on the roof of the mouth, and the eyelids may look puffy.

The spleen may enlarge without causing symptoms. If discomfort occurs, it may be felt in the upper left side of the abdomen. The liver can also become inflamed. This sometimes causes nausea, discomfort under the right ribs, dark urine, pale stools, or jaundice, which is yellowing of the skin or whites of the eyes.

A widespread rash can occur. It is particularly associated with taking ampicillin or amoxicillin during mono, although other rashes are possible.

The fever and sore throat often improve within a few weeks. Tiredness may last for several more weeks and sometimes for months. Persistent tiredness does not automatically mean that the infection is still active.

EBV causes most cases of infectious mononucleosis. It belongs to the herpesvirus family. After the first infection, the virus remains inactive, or dormant, in certain immune cells for life. This is common and usually causes no further health problems.

EBV can occasionally reactivate and appear in saliva without causing symptoms. Because people may release the virus before, during, and long after illness, it is often impossible to identify exactly when or from whom it was acquired.

Other infections can cause a similar group of symptoms, sometimes called a mononucleosis-like illness. These include cytomegalovirus, toxoplasmosis, acute HIV, and some other viral infections. Testing helps distinguish among them when this would affect care.

Factors associated with developing noticeable mono include:

• First acquiring EBV during adolescence or young adulthood
• Close contact with another person's saliva
• Sharing drinks, utensils, toothbrushes, or similar personal items
• Living or socialising in settings where close contact is common

Mono is not simply caused by being run down or under stress. However, illness-related fatigue may feel more difficult to manage when sleep is poor or daily demands are high.

A healthcare professional will ask about the symptoms, when they started, and possible exposures. They may examine the throat, neck lymph nodes, abdomen, liver, and spleen.

Blood tests may be used when the diagnosis is uncertain or confirmation would guide activity restrictions and follow-up. A heterophile antibody test, sometimes called a Monospot test, can support the diagnosis. However, it may be negative early in the illness and is less reliable in young children.

EBV-specific antibody tests can show whether an infection is recent, occurred in the past, or is unlikely. These tests look at the immune system's response to different parts of the virus.

A complete blood count may show an increased number of lymphocytes, a type of white blood cell, including cells described as atypical lymphocytes. This finding supports mono but does not confirm EBV by itself.

Liver blood tests may be temporarily abnormal. Depending on the symptoms, testing for strep throat, COVID-19, cytomegalovirus, HIV, or other conditions may be appropriate.

Imaging is not routinely needed. An ultrasound can measure the spleen, but normal spleen size differs among people, so ultrasound alone cannot always determine when returning to sport is safe.

There is no routine medicine that removes EBV from the body. Treatment focuses on comfort, hydration, recovery, and preventing injury to an enlarged spleen.

Helpful measures include:

• Resting as needed while gradually returning to ordinary activity
• Drinking enough fluid to keep urine pale
• Using appropriate non-prescription medicine for pain or fever
• Trying warm drinks, cold foods, or salt-water gargles for throat discomfort
• Avoiding alcohol while unwell, particularly if liver tests are abnormal

Follow package directions for non-prescription medicines. Some products contain the same pain reliever, so combining cold remedies can accidentally lead to taking too much. Aspirin should not be given to children or teenagers with a viral illness because of the risk of Reye syndrome, a rare but serious condition.

Antibiotics do not treat EBV. They are only useful if a separate bacterial infection, such as confirmed strep throat, is present. Ampicillin and amoxicillin commonly trigger a rash when taken during mono. This rash does not always mean there is a lasting penicillin allergy, but it should be reviewed before future antibiotic use.

Corticosteroids like prednisone or hydrocortisone, which reduce inflammation, are not routine treatment for uncomplicated mono. A clinician may use them for specific serious problems, such as severe swelling that threatens the airway or certain blood complications. Antiviral medicines are also not routinely recommended for ordinary mono.

Because of the risk of spleen injury, strenuous exercise, heavy lifting, and sports should be avoided during early recovery. Current sports medicine guidance generally excludes athletic activity for the first three weeks after symptoms begin. Return should then be gradual and only when you are fever-free and feel clinically well. Contact or collision sports require particular caution and professional guidance.

Most people recover without serious complications. When complications occur, they may involve the spleen, airway, liver, blood, or nervous system.

An enlarged spleen can tear or rupture. This is uncommon but can cause internal bleeding. Warning signs include sudden or worsening pain in the upper left abdomen, pain felt at the tip of the left shoulder, dizziness, weakness, or fainting. A rupture can occur after a blow to the abdomen, but sometimes no injury is recalled.

Severely enlarged tonsils can narrow the airway. Increasing difficulty breathing, noisy breathing, or being unable to swallow saliva requires emergency assessment.

Other possible complications include:

• Liver inflammation or jaundice
• Dehydration because swallowing is painful
• Low numbers of red blood cells or platelets
• Inflammation affecting the heart or nervous system
• A secondary bacterial throat infection

Long-lasting symptoms are not usually caused by continued active mono. Rare EBV-related conditions exist, but they are different from the usual slow recovery after infectious mononucleosis.

There is no licensed vaccine that prevents EBV infection, and mono cannot always be prevented. People can spread EBV without knowing they carry it.

To reduce exposure to saliva, avoid sharing drinks, utensils, lip products, toothbrushes, or similar personal items. Avoid kissing while you are acutely unwell. Wash items that have been in contact with saliva.

There is no exact date when a person stops being contagious. EBV may remain in saliva for months and can later appear again without symptoms. For this reason, prolonged isolation is not practical or usually recommended. Regular handwashing and avoiding saliva-sharing behaviours are more useful.

The sore throat and fever commonly settle before the tiredness does. During the first few weeks, you may need more sleep and may find school, work, exercise, or household tasks harder than usual.

Recovery is usually gradual. Trying to resume a full schedule as soon as the fever stops may leave you exhausted. It can help to restart with shorter days, lighter tasks, and planned rest. Gentle daily activity may be reasonable once you feel able, but it should not include early strenuous exercise or activities that could injure the abdomen.

Many people are substantially better within two to four weeks. Fatigue can continue for several additional weeks and, in some cases, for months. The pace is different for each person, and a slower recovery does not necessarily predict a permanent problem.

Once the acute condition has resolved, EBV remains dormant in the body. Most people do not develop mono again. A later episode of similar symptoms may have another cause and should not automatically be assumed to be EBV.

Routine follow-up may be useful if symptoms are not improving, fatigue is interfering with daily life, liver tests need rechecking, or you need guidance about returning to strenuous work or sport.

Arrange a routine medical assessment if you think you may have mono, especially if you have a severe sore throat, swollen neck glands, ongoing fever, or fatigue that is disrupting daily activities. Testing may be needed because several infections can cause similar symptoms.

Seek prompt medical advice if:

• You cannot drink enough or are passing very little urine
• Fever or throat symptoms are worsening rather than improving
• Your skin or eyes become yellow
• Abdominal discomfort develops
• Symptoms improve and then return
• Fatigue remains severe or unexplained over time

Call emergency services for:

• Sudden or severe upper-left abdominal pain
• Abdominal pain with left shoulder pain, dizziness, or fainting
• Trouble breathing or noisy breathing
• Inability to swallow saliva
• Confusion, collapse, or a seizure

These symptoms can indicate spleen rupture, severe airway swelling, or another complication requiring immediate assessment.

How long is mono contagious?

EBV can be present in saliva before symptoms begin and for months afterward. It may also appear in saliva later without causing illness. There is no reliable day when transmission risk becomes zero. Avoid sharing saliva, but prolonged isolation is generally unnecessary.

Can you get mono twice?

Most people have one episode caused by their first EBV infection. EBV remains dormant afterward, but a second typical episode is unusual. Similar symptoms later may be caused by another infection or condition.

When can I go back to school or work?

You can often return when the fever has settled, you can drink and eat adequately, and your energy allows you to manage the day. A gradual return or shorter schedule may help. Returning to school or desk work is different from returning to strenuous activity.

When can I exercise or play sports again?

Avoid athletic activity during the first three weeks from symptom onset. After that, light non-contact activity may be considered if you are fever-free and feel well. Contact sports, collision sports, heavy lifting, and strenuous exercise need more caution because the spleen may still be enlarged.

Does an amoxicillin rash mean I am allergic to penicillin?

Not always. A widespread rash is common when amoxicillin or ampicillin is taken during mono. Tell healthcare professionals about the reaction, but do not assume a permanent allergy without appropriate review.

Is mono a sexually transmitted infection?

Mono is not usually classified as a sexually transmitted infection. EBV spreads mainly through saliva, so kissing can transmit it. Sexual contact may also involve saliva and other body fluids, but sex is not required for infection.