Infectious Mononucleosis (Mono)

How mono spreads

EBV spreads mainly through saliva: kissing, sharing cups, bottles, utensils or toothbrushes. It can also spread through blood and semen, and from transplants. The incubation period is long, about 4 to 6 weeks between exposure and symptoms.

People can shed virus in saliva for months after recovery, and intermittently for life, so outbreaks are hard to prevent. Most adults worldwide have been infected with EBV by middle age, many without ever knowing it. Once infected, the virus stays dormant in the body, and people rarely get mono twice.

Symptoms

Symptoms build over several days:

• fatigue, often severe
• fever
• severe sore throat, with swollen tonsils that may be covered in white patches
• swollen lymph nodes, especially at the back and sides of the neck, also in armpits and groin
• headache and body aches
• loss of appetite
• swelling around the eyes
• enlarged spleen, in about half of people; sometimes an enlarged liver
• a rash, especially after taking amoxicillin or ampicillin

Young children often have mild symptoms resembling a cold. Older adults may have more fever and liver involvement and less sore throat.

Mono vs strep throat

Both can occur together, so a strep test may be done as well.

Diagnosis

• Physical exam: throat, lymph nodes, spleen and liver.
• Monospot (heterophile antibody) test: rapid but may be negative in the first week and in children under 4.
• EBV-specific antibody tests: confirm recent infection when the monospot is negative.
• Blood count: raised lymphocytes with atypical forms.
• Liver tests: often mildly raised.
• Strep test if strep throat is also possible.

Treatment

There is no antiviral treatment for routine mono. Care focuses on symptoms:

• Rest as needed; strict bed rest is not necessary.
• Fluids to prevent dehydration.
• Pain and fever relief: acetaminophen (paracetamol) or ibuprofen. Follow the label dose. Do not give aspirin to children or teenagers because of the risk of Reye syndrome.
• Sore throat relief: salt water gargles, throat lozenges for older children and adults, cold drinks and soft foods.
• Steroids: used only for complications such as tonsils swelling enough to threaten the airway.
• Antibiotics do not help and are only used for a confirmed bacterial infection such as strep. Amoxicillin and ampicillin commonly cause a rash in mono, which is not usually a true allergy.

Sports and activity

The spleen can enlarge and become fragile, even without symptoms. Avoid contact sports, heavy lifting and strenuous activity for at least 3 to 4 weeks from the start of symptoms, and longer if the spleen is still enlarged, as advised by your doctor. Return gradually.

School and work

People can return when they feel well enough. There is no need to isolate, but avoid kissing and sharing drinks, utensils or toothbrushes for several weeks.

Complications

• Ruptured spleen: rare (under 1%), but an emergency; most occur in the first 3 weeks.
• Airway obstruction from severely swollen tonsils.
• Hepatitis and jaundice, usually mild.
• Low blood counts: anemia or low platelets.
• Neurological complications: rare, including meningitis, encephalitis and Guillain-Barre syndrome.
• Prolonged fatigue: some people, especially adolescents, have fatigue for months; a small number go on to meet criteria for chronic fatigue syndrome.

Research has also linked past EBV infection to a higher risk of multiple sclerosis and some lymphomas, though most people with EBV never develop these.

Prevention

There is no vaccine. Avoid sharing drinks, utensils and toothbrushes, and avoid kissing people who are sick. Wash hands regularly.

Frequently asked questions

How long does mono last?

Fever and sore throat usually improve within 1 to 2 weeks, and most people feel better within 2 to 4 weeks. Fatigue can last several weeks to months, especially in teenagers. Recovery is gradual.

How long is mono contagious?

Virus is shed in saliva from before symptoms start until at least several weeks to months after recovery, and on and off for life. Avoid kissing and sharing drinks or utensils for several weeks after symptoms resolve.

Can you get mono twice?

It is rare. After infection, EBV stays dormant in the body and the immune system usually keeps it controlled. Occasionally, mono-like illness occurs from a different virus, such as cytomegalovirus.

When can I play sports after mono?

Most guidelines advise avoiding contact sports and strenuous activity for at least 3 to 4 weeks from symptom onset, because of the risk of spleen rupture. Your doctor may advise longer if your spleen is still enlarged. Return gradually.

Why did I get a rash from amoxicillin with mono?

Many people with mono develop a widespread itchy rash after taking amoxicillin or ampicillin. It is a reaction linked to the viral infection and usually not a true penicillin allergy, but tell your doctor so it can be assessed.