Infectious Mononucleosis

Infectious mononucleosis is most commonly caused by the Epstein–Barr virus (EBV), which spreads primarily through saliva—kissing, sharing utensils, or drinks. Less commonly, cytomegalovirus and other viruses cause a similar illness. EBV infects B cells and throat cells, then spreads via lymphocytes; close contact and adolescence/young adulthood increase transmission risk, and infections are often asymptomatic in children.

The best treatment for infectious mononucleosis is supportive: rest, plenty of fluids, throat soothing measures, and pain/fever relief with acetaminophen or NSAIDs. Corticosteroids are used only for severe throat swelling or airway compromise. Antibiotics aren’t helpful unless there’s a bacterial infection (amoxicillin often causes a rash in mono). Avoid contact sports for at least 3–4 weeks due to spleen rupture risk.

The hallmark of infectious mononucleosis is marked fatigue with sore throat and tender posterior cervical lymphadenopathy, often accompanied by fever, pharyngitis, and splenomegaly. Laboratory features include atypical (reactive) lymphocytosis and positive heterophile (Monospot) antibodies, which help confirm Epstein–Barr virus–related mononucleosis. Symptoms typically develop 4–6 weeks after exposure and can last several weeks to months.

Mononucleosis (EBV) spreads through saliva. People are most contagious during the acute symptomatic phase—typically two to four weeks—but viral shedding can continue for several months after recovery and intermittently for life. Incubation is usually four to six weeks. To reduce spread, avoid kissing, sharing utensils, and close saliva exposure while symptomatic and for several weeks afterward; immunocompromised people may shed longer.

Early signs of mono often include extreme fatigue, a sore throat (sometimes with white patches), fever, and tender, swollen lymph nodes in the neck. Other initial symptoms can be headache, loss of appetite, muscle aches and swollen tonsils; some people also develop a skin rash. Symptoms usually build gradually over days to weeks.

Infectious mononucleosis (mono), usually caused by Epstein–Barr virus, is typically mild and self-limiting with fever, sore throat, fatigue and swollen lymph nodes. Most recover with rest, fluids and symptom relief. Serious complications are uncommon but can include enlarged spleen with risk of rupture, airway obstruction, liver inflammation, or neurological problems—seek urgent care for severe breathing, abdominal pain, jaundice or very high fever.