A Brief Recap of Infectious Mononucleosis in Athletes cover

A Brief Recap of Infectious Mononucleosis in Athletes

Mono, or infectious mononucleosis, sometimes referred to as ‘kissing disease’ is a viral triad of pharyngitis, fever and cervical lymphadenopathy caused by the epstein-barr virus (EBV) and typically seen in teenagers or young adults. As many as 50% of college freshmen are susceptible to infection and the annual incidence in that age group is estimated to be between 1-3% [1]. By late adulthood, up to 90% of adults have been infected although many may never develop symptoms.

Case Vignette

You are caring for a 16 year old high school athlete with mono. The athlete is anxious to return to play as the playoffs begin next week. Which of the following is considered the best guidance for athletes returning to light, non-contact activities from a mononucleosis infection?

A) Weekly ultrasound until the spleen is less than 7 cm
B) 3 weeks from the onset of symptoms
C) Until the spleen is no longer palpable
D) 6 weeks from the onset of symptoms

Transmission primarily occurs through oral secretions, although it can be shared through coughing, sneezing and other forms of close contact. Less commonly, EBV is transmitted through blood, solid organ and/lor hematopoietic cell transplant. In general, the illness is self limited with a long incubation period of 30-50 days which can make contact tracing challenging.
Acutely, patients may endorse a prodrome of fever, headache and malaise. The more classic triad of fever, pharyngitis and lymphadenopathy is only seen in about half of cases. Patients may also have palatal petechiae and a maculopapular truncal rash, especially if exposed to amoxicillin or ampicillin. Of note, this is not considered an allergic reaction to the medication but an interaction with viral shedding. Splenomegaly is seen in up to 50% of patients and will be discussed in more detail below Less commonly you may see jaundice (especially in older adults), periorbital edema, CNS complications and myocarditis. Diagnosis is primarily clinical but confirmed with a positive heterophile antibody test and supported by a leukocytosis with a predominance of lymphocytes and atypical lymphocytes.
illustration of mononucleosis symptoms mono athlete sports

Figure 1. Illustration of mononucleosis symptoms (courtesy of everydayhealth.com)

In athletes, the most concerning complication is splenomegaly and the risk of splenic rupture. This presents several challenges. The first is determining if the patient has splenomegaly. Physical exam has a poor sensitivity, specificity and inter-rater reliability for detecting splenomegaly. CT and US are the most well studied imaging modalities. CT providers more organ detail and better quantification of spleen size, but is limited by cost, time and radiation exposure. Ultrasound also allows quantification of the spleen and serial exams can be performed to assess changes as the disease progresses and resolves. The biggest limitation of ultrasound is that there is no normative data on spleen size. CT is the imaging modality of choice in suspected splenic rupture. The presence of splenomegaly and the risk of splenic rupture are not clearly directly linked and the relationship is considered controversial. Finally, the role of imaging in splenomegaly has not been well delineated.
Management of mononucleosis is primarily supportive as the disease is self limited with no curative treatment. Odynophagia should be treated with analgesics, salt water gurgles, throat lozenges and viscous lidocaine. There is no role for acyclovir. Oral corticosteroids may be useful in athletes with impending airway obstruction, hemolytic anemia, severe thrombocytopenia, or myocarditis [2]. Athletes should be removed from play when the diagnosis is suspected or confirmed. They should avoid penicillin antibiotics, aspirin due to risk of thrombocytopenia and acetaminophen and alcohol due to risk of hepatotoxicity.
Return to play is perhaps the most challenging and controversial aspect of managing athletes with infectious mononucleosis. The risk of splenic rupture in the athletic population is not well studied, but is 0.1% – 0.5% in the general population. In the case of splenic rupture, Sylvester et al found the vast majority of cases occur within the first 31 days, although there are case reports up to 7 weeks [3]. Physicians should consider allowing athletes to return to light, non contact activities after 3 weeks [4]. When to allow athletes to return to contact sports is more controversial. Expert opinion varies between 4 and 6 weeks although and based on the Sylvester data set we would recommend 31 days. In any event, return to play must be individualized to the athletes and risks and benefits of return to play should be discussed.

Case Conclusion

Answer is B, 3 weeks from symptom onset. This is controversial. The incidence of splenic rupture is 01%-0.5% in the general population and poorly understood in the athletic population. The majority of cases of splenic rupture occur within the first 31 days, although they can occur as late as 7 weeks (Sylvester, 2019). Physicians should consider allowing athletes to begin light, non-contact activity around 3 weeks with the goal of returning to full contact somewhere between 31 days and 6 weeks (Putukian 2008). There is no evidence supporting use of sonographic size of the spleen or palpation of the spleen to guide return to play.


[1] Brodsky AL, Heath CW. Infectious mononucleosis; epidemiological patterns at United States colleges and universities. Am J Epidemiol. 1972;96:87–93.
[2] Candy B, Hotopf M. Steroids for symptom control in infectious mononucleosis. Cochrane Database Syst Rev. 2006;3:CD004402
[3] Sylvester, J. E., Buchanan, B. K., Paradise, S. L., Yauger, J. J., & Beutler, A. I. (2019). Association of Splenic Rupture and Infectious Mononucleosis: A Retrospective Analysis and Review of Return-to-Play Recommendations. Sports Health, 11(6), 543–549.
[4] Putukian, Margot, et al. “Mononucleosis and athletic participation: an evidence-based subject review.” Clinical Journal of Sport Medicine 18.4 (2008): 309-315.