The prognosis for healthy people with IM is very good. Death occurs rarely, and is usually caused by airway obstruction, splenic rupture, neurological complications, haemorrhage, or secondary infection.
Post-infective chronic fatigue syndrome (CFS)
The reported frequency of this syndrome in patients with history of IM varies in different sources, but overall it is not considered very common. Several small studies raise the possibility that Epstein-Barr virus (EBV) may play some role in the pathogenesis of CFS in subsets of these patients.[71]Zhang L, Goudth J, Christmas D, et al. Microbial infections in eight genomic subtypes of chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME). J Clin Pathol. 2010 Feb;63(2):156-64.
https://jcp.bmj.com/content/63/2/156.long
http://www.ncbi.nlm.nih.gov/pubmed/19955554?tool=bestpractice.com
[72]Lerner AM, Beqaj SH, Deeter RG, et al. Valacyclovir treatment in Epstein-Barr virus subset chronic fatigue syndrome: thirty-six months follow-up. In Vivo. 2007 Sep-Oct;21(5):707-13.
http://iv.iiarjournals.org/content/21/5/707.long
http://www.ncbi.nlm.nih.gov/pubmed/18019402?tool=bestpractice.com
[73]Kogelnik AM, Loomis K, Hoegh-Peterson M, et al. Use of valganciclovir with elevated antibody titers against Human herpesvirus-6 (HHV-6) and Epstein-Barr virus (EBV) who were experiencing central nervous system dysfunction including long-standing fatigue. JJ Clin Virol. 2006 Dec;37(suppl 1):S33-8.
http://www.ncbi.nlm.nih.gov/pubmed/17276366?tool=bestpractice.com
No strong data exist to date to routinely implicate EBV an aetiological agent of this highly publicised syndrome.[48]Katz BZ. Update on chronic fatigue syndrome and Epstein-Barr virus. Pediatr Ann. 2002 Nov;31(11):741-4.
http://www.ncbi.nlm.nih.gov/pubmed/12455482?tool=bestpractice.com
Rather, new evidence suggests that post-infective CFS represents a common and stereotyped outcome from several viral and non-viral infections.[74]Hickie I, Davenport T, Wakefield D, et al. Post-infective and chronic fatigue syndromes precipitated by viral and non-viral pathogens: prospective cohort study. BMJ. 2006 Sep 16;333(7568):575.
http://www.bmj.com/cgi/content/full/333/7568/575
http://www.ncbi.nlm.nih.gov/pubmed/16950834?tool=bestpractice.com
In a longitudinal cohort study, about half of younger patients with CFS after IM with long-term incapacity for work experienced marked improvement, including full-time or part-time employment, thus showing better outcomes than expected.[75]Nyland M, Naess H, Birkeland JS, et al. Longitudinal follow-up of employment status in patients with chronic fatigue syndrome after mononucleosis. BMJ Open. 2014 Nov 26;4(11):e005798.
http://bmjopen.bmj.com/content/4/11/e005798.long
http://www.ncbi.nlm.nih.gov/pubmed/25428629?tool=bestpractice.com