Of course to cure from a fever in general takes already time to recover from, but in the kissing disease it takes often much longer (sometimes even years) and the tiredness is much more a symptom of the Epstein virus than other virus infections. But what causes this precisely?

  • 1
    The premise of this question is somewhat incorrect. EBV does not cause more post-infection symptoms than every other viral infection. There are some viral (and some bacterial) infections that are comparable in this regard. So I suspect the mechanisms are somewhat non-specific. Commented Jan 25, 2021 at 16:58
  • I'm not sure how the numbers compare precisely/directly, but SARS and Covid-19 also cause such fatigue. For SARS it was something like 25% of those infected who experienced post-viral fatigue kcl.ac.uk/… Commented Jan 25, 2021 at 17:18
  • Likewise for Ebola, some 28% reported such post-infection fatigue. The incidence from EBV seems somewhat lower at 4-13% (depending on the time frame) tandfonline.com/doi/full/10.1080/21641846.2020.1778227 Commented Jan 25, 2021 at 17:31

2 Answers 2


There is no consensus on the exact cause, although in Chronic Epstein-Barr Activation (CEBA) it has been linked to the effects of inflammation (eg a cytokine storm), plus immune activation and tryptophan degradation.

In the more common, non-CEBA Epstein-Barr infection immune system responses are also suggested to be linked to the fatigue. "Presently, therefore the is no proven fatigue-causing substance or fatigue transmitting substance. However, the most probable candidates for such fatigue-inducing or fatigue transmitting substances are cytokines, including interferon."2

Lasting fatigue is found in a number of viruses, including a number of Covid-19 patients.3 This may be related to Interleukin-1 levels, an inflammatory cytokine.

Long term fatigue is often termed "Chronic fatigue", "post-fatigue infection" or "post-viral fatigue" (without the syndrome part).

  • 1
    It's important to note that Chronic active Epstein-Barr virus (CAEBV) infection is a rare and life-threatening condition where the virus is never brought under control. Also I agree that Long term fatigue = Chronic fatigue, but long term fatigue is not synonymous with post-infectious fatigue/post-viral fatigue. CFS is considered a type of post-infectious fatigue though according to your 2nd source.
    – D.Tan
    Commented Jul 9, 2020 at 20:46

According to Emedicine medscape:

Appreciate that EBV may trigger chronic fatigue, but it does not cause chronic fatigue.

In their page on Chronic Fatigue Syndrome:

CFS is a biological illness, not a psychologic disorder. The exact pathogenesis is unknown. Numerous mechanisms and molecules have been implicated that lead to abnormalities in immune dysfunction, hormonal regulation, metabolism and response to oxidative stress to include impaired natural killer cell function and/or T-cell function, elevated cytokines, and autoantibodies (rheumatic factor, antithyroid antibodies, antigliadin, anti–smooth muscle antibodies, and cold agglutinins). [3, 4] Infections have been suspected; however, no causal role has been established.

The sources cited:

  1. https://www.cdc.gov/me-cfs/index.html
  2. https://www.ncbi.nlm.nih.gov/pubmed/28760971
  • The question asked about tiredness in EBV, not cases of CFS resulting from EBV. CFS cannot be diagnosed until after the virus has cleared.
    – Mousey
    Commented Jul 4, 2020 at 13:17
  • I agree with you that CFS is something that would occur after an EBV infection resolves. I had interpreted the questions as asking for a reason for long-term tiredness after an EBV infection.
    – D.Tan
    Commented Jul 9, 2020 at 20:29

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