Could COVID Wake Up the Virus Behind Glandular Fever? What the Evidence Really Shows
Could COVID Wake Up the Virus Behind Glandular Fever? What the Evidence Really Shows
From early in the pandemic, it became obvious that COVID-19 was not always a short-lived respiratory illness. For some people, the infection was followed by weeks or months of fatigue, brain fog, poor stamina and a lingering sense that the body had not fully recovered.
That persistence has led scientists to ask a more complicated question: what if some of the ongoing symptoms are not caused by the coronavirus alone, but by the way it disturbs the immune system?
One virus has become especially relevant to that discussion: Epstein-Barr virus, or EBV. It is the virus best known for causing glandular fever, but what makes it particularly important is that it does not simply disappear after the first infection. Like other herpesviruses, it can remain latent in the body and reactivate later under certain conditions.
The evidence supplied here suggests COVID-19 may be linked to that sort of reactivation — or at least to immune disruption that makes EBV activity more likely. That is not the same thing as proving that COVID-19 directly causes classic glandular fever in large numbers of people. But it does support an increasingly important idea in post-viral medicine: SARS-CoV-2 may, in some cases, unsettle the body enough to let old infections resurface.
Why Epstein-Barr keeps appearing in the COVID conversation
EBV is extraordinarily common. Most people are infected at some point in life, often in childhood or adolescence. In some people it causes glandular fever, with symptoms such as fever, sore throat, swollen glands and profound fatigue. In many others, the initial infection is mild or barely noticed.
What matters for this story is what happens afterwards.
Once the first infection settles, EBV can remain dormant in the body for years. It is not truly gone. It is simply kept under control by the immune system. If that control weakens or becomes dysregulated, the virus can reactivate.
That does not necessarily mean someone will develop a textbook case of glandular fever again. Reactivation can be more subtle than that. It may show up as detectable viral activity, shifts in immune markers or symptoms that overlap with other post-viral syndromes.
This is exactly why COVID-19 has attracted attention. Researchers do not need SARS-CoV-2 to create a brand-new EBV infection from scratch in order for it to matter. A more plausible concern is that it may disrupt immune balance enough to allow a latent virus to become active again.
What the research actually supports
The most relevant study in the evidence provided found that Epstein-Barr virus viraemia at the time of COVID-19 diagnosis was one of several factors associated with later post-acute COVID-19 sequelae. Put simply, people who showed signs of EBV activity when they were diagnosed with COVID-19 appeared more likely to experience lingering symptoms afterwards.
That is an important finding because it suggests a biological link between SARS-CoV-2 infection and EBV activity. It does not prove that EBV is responsible for all long-term symptoms. It does not prove that COVID-19 is creating a wave of new glandular fever diagnoses. But it does support the idea that the virus behind glandular fever may form part of the wider post-COVID picture in at least some patients.
The second source provided, a broader review on COVID-19 and carcinogenesis, is less directly focused on glandular fever. It discusses co-infections with oncogenic viruses such as EBV as part of the wider long-term consequences of immune disruption after COVID-19. While that is not direct evidence of clinical mononucleosis after infection, it does reinforce the broader biological plausibility that SARS-CoV-2 may alter the body’s relationship with latent viruses.
Taken together, the literature supports an association and a credible mechanism. What it does not yet support is a straightforward claim that COVID-19 directly causes infectious mononucleosis in a clear epidemiological sense.
Why this matters for long COVID
One reason the EBV hypothesis has attracted so much interest is that it may help explain part of the long COVID puzzle.
Many symptoms reported in post-acute COVID syndromes — particularly severe fatigue, reduced exercise tolerance, cognitive difficulty and a lingering post-illness crash — overlap with symptoms often associated with glandular fever or EBV-related illness. That does not mean the conditions are identical. Long COVID is likely a complex syndrome with multiple drivers, including inflammation, vascular changes, autonomic dysfunction, tissue injury and persistent immune activation.
But EBV reactivation may be one part of that larger picture.
That matters because it offers a more biologically grounded explanation for symptoms that have sometimes been difficult to categorise. It shifts the conversation away from the idea that patients are merely “recovering slowly” in some vague sense, and towards the possibility that measurable post-viral interactions are taking place.
Why the headline still needs careful handling
This is where the evidence becomes easy to overstate.
The supplied PubMed studies do not directly investigate incident glandular fever after COVID-19 in a large population cohort. They do not provide absolute risk figures. They do not tell us how often clinically diagnosed glandular fever occurs after SARS-CoV-2 infection. And the most relevant paper focuses on post-acute COVID symptoms and EBV viraemia, not on classical infectious mononucleosis as a main outcome.
That means the strongest version of the headline — that COVID-19 increases the risk of glandular fever in a direct and proven way — reaches further than the evidence available here.
A more accurate interpretation is that COVID-19 may be linked to Epstein-Barr reactivation or EBV-related immune disturbances, and that this may help explain some symptoms that persist after infection.
That is still clinically interesting. It is simply more nuanced than the headline suggests.
What this could mean for patients
For people who continue to feel unwell after COVID-19, this research offers two messages.
The first is validating: ongoing fatigue, brain fog and post-viral malaise may have real biological underpinnings even when standard tests do not immediately provide an answer. The interaction between SARS-CoV-2, immune dysregulation and latent viruses is one plausible explanation.
The second is practical: not every case of prolonged symptoms after COVID-19 should be assumed to be EBV reactivation or glandular fever. Fatigue and poor recovery can stem from many overlapping causes, including autonomic problems, cardiovascular effects, sleep disruption, respiratory limitations, endocrine changes and mental health strain.
So this is a clue, not a diagnosis.
Why this story is bigger than one virus
The broader importance of this line of research is that it changes how medicine thinks about post-viral illness.
For a long time, infections were often framed as isolated events: a virus appears, causes symptoms, and is cleared. COVID-19 has shown that in some people the aftermath may be far more complicated. One infection may disturb immune control over multiple other biological processes, including the behaviour of latent viruses that had previously remained quiet.
If that idea holds up, it could reshape how clinicians understand recovery, long COVID and post-viral syndromes more generally. It may also help explain why two people can catch the same virus and follow very different paths afterwards.
For the UK, where long COVID continues to place pressure on patients, GPs and specialist services, that distinction matters. It influences how persistent symptoms are interpreted, how they are validated and what kinds of biological markers researchers will need to study next.
The most grounded takeaway
The evidence here is weak and indirect, but it points in a coherent direction. COVID-19 may help reactivate Epstein-Barr virus — or at least create the sort of immune disturbance in which EBV becomes more active.
That does not amount to proof that COVID-19 is causing classic glandular fever in a simple, large-scale way. It does not tell us how common the risk is, and it does not settle whether EBV is driving symptoms, acting as a marker of immune stress or forming just one part of a broader post-viral process.
What it does offer is an important clue about how COVID-19 may continue to affect the body after the acute infection has passed.
This is not just a story about glandular fever. It is a story about what happens when one virus disrupts the body enough to let old infections speak up again. And that may prove to be one of the most revealing lessons of the post-COVID era.