Have you Heard About the Epstein-Barr Virus?

The Common Virus That Might Change Medicine

What 95% of adults carry — and why researchers are racing to develop a vaccine.

Author: Paola Larrabure, Pharma Content Manager  |  Clinical Reviewer: Julia Kravtsova, PharmD, Head Patient Navigator

Last Reviewed: April 2026

If you’ve ever had mono — that relentless exhaustion, the sore throat that wouldn’t quit, the swollen lymph nodes that lingered for weeks — you’ve already met the Epstein-Barr virus. If you haven’t had mono, you’ve likely still encountered EBV. The virus infects roughly 95% of adults worldwide. Most people contract it in childhood or adolescence, often without noticing. Once it’s in the body, it stays there for life, usually dormant.

For decades, EBV was considered mostly harmless after the initial infection passed. A nuisance virus. The cause of a few miserable weeks as a teenager. That understanding is being fundamentally rewritten. In the past five years, landmark research has linked EBV to multiple sclerosis, several types of cancer, long COVID, chronic fatigue syndrome, and a growing list of autoimmune conditions. Pharmaceutical companies are now racing to develop the first-ever EBV vaccine. And clinicians are starting to take chronic and reactivated EBV far more seriously than they ever did before.

This guide walks through what EBV is, how it behaves in the body, what recent research has revealed about its connection to serious disease, and what’s happening on the vaccine front. It is written for patients, caregivers, and anyone who has had mono and wondered whether it matters long-term. It is not a substitute for medical advice — if you have questions about EBV and your health, please speak with your doctor.

What is Epstein-Barr virus?

Epstein-Barr virus is a member of the herpesvirus family — the same family that includes oral herpes (HSV-1), genital herpes (HSV-2), chickenpox/shingles (varicella-zoster virus), and cytomegalovirus (CMV). EBV was first identified in 1964 by researchers Michael Anthony Epstein, Yvonne Barr, and Bert Achong, who discovered it in cells from a tumor type called Burkitt lymphoma. It was the first human virus ever shown to cause cancer.

What makes herpesviruses distinct from other viruses — and what makes EBV particularly interesting — is their ability to establish lifelong latent infection. After the initial infection, EBV doesn’t leave. It takes up residence in a specific type of immune cell called a B lymphocyte (B cell), where it can remain quietly for decades. For most people, this latency causes no obvious problems. But the virus is not truly inert. Under certain conditions — stress, other infections, immune suppression — EBV can reactivate, and that reactivation is increasingly understood to play a role in a range of serious health conditions.

How EBV spreads and what happens in the body

EBV is primarily transmitted through saliva, which is why it’s sometimes called “the kissing disease.” But it can also spread through other bodily fluids, including blood and semen, and through shared items like drinking glasses or toothbrushes. Transmission usually happens in close contact — within families, among teenagers and young adults, in schools and college dormitories.

Once EBV enters the body, it infects epithelial cells lining the throat and then spreads to B lymphocytes. In most people, the immune system responds aggressively, and within a few weeks the acute infection is controlled. But the virus doesn’t get eliminated — it settles into a latent state inside memory B cells, where it can periodically reactivate throughout life. For most healthy people, these reactivation events are silent: the immune system keeps the virus in check without the person ever knowing.

The problem is that this cycle of latency and periodic reactivation gives the virus many opportunities to interact with the immune system over a lifetime. In genetically susceptible individuals, those interactions appear to be where disease develops.

Mononucleosis — the acute illness most people know

When EBV is contracted in childhood, symptoms are often mild or absent — a cold-like illness that resolves without anyone identifying the cause. When the infection happens for the first time in adolescence or young adulthood, however, the body’s response is often much more dramatic, producing the classic symptoms of infectious mononucleosis (often called “mono” or “glandular fever”):

• Severe fatigue that can last for weeks or months
• Sore throat
• Fever
• Swollen lymph nodes, especially in the neck
• Swollen tonsils
• Enlarged spleen
• Liver inflammation in some cases
• Headache
• Body aches
• Loss of appetite

There is no specific antiviral treatment for mono in most cases. Treatment is supportive — rest, hydration, pain and fever management. Most people recover fully within several weeks, though fatigue can linger for months. In a small percentage of patients, prolonged post-infection symptoms can persist for six months or longer, and some of those patients go on to develop chronic fatigue syndrome or myalgic encephalomyelitis (ME/CFS).

Historically, mono was considered a self-limited illness that cleared and was done. Modern research is revealing that the long-term implications may be far more significant for some patients — especially those with certain genetic factors or other risk profiles.

The EBV-multiple sclerosis connection

The most striking recent discovery about EBV is its role in multiple sclerosis. In January 2022, a team of researchers led by Dr. Alberto Ascherio at Harvard T.H. Chan School of Public Health published a landmark study in Science analyzing data from more than 10 million active-duty U.S. military personnel over 20 years. The findings were remarkable: the risk of developing MS increased 32-fold after EBV infection. No other viral infection showed a similar association. The authors concluded that EBV is very likely a cause of MS — the first such virus-disease causal link of this magnitude to be established for an autoimmune disease.

Just days after that study, a separate research team at Stanford Medicine led by Dr. William Robinson published research in Nature providing a biological mechanism. They found that part of the EBV virus looks structurally similar to a protein found in the brain and spinal cord — a phenomenon called molecular mimicry. When the immune system produces antibodies against EBV, those antibodies can mistakenly attack the body’s own nervous system tissue. Approximately 20 to 25 percent of MS patients carry antibodies that bind to both EBV and to brain tissue.

The research has continued to accelerate:

• February 2026 — Researchers at UC San Francisco published findings in Nature Immunology showing that certain “killer” T cells (CD8+ T cells) that specifically target EBV accumulate in large numbers in the brain and spinal fluid of MS patients — far more than in their blood. One viral gene was active only in people with MS. This suggests EBV may be doing more than just triggering MS at the start — it may be actively driving ongoing disease activity.
• January 2026 — A study in Cell demonstrated how EBV infection combined with a specific genetic variant (HLA-DR15) drives MS through presentation of myelin peptides to the immune system.
• Studies have also shown that people who have never been infected with EBV almost never develop MS. Essentially, EBV infection appears to be a prerequisite for MS.

This research completely reshapes how we think about MS prevention and treatment. If EBV is a cause, then preventing EBV infection — or controlling it once it’s established — could theoretically prevent or slow MS. That is exactly what pharmaceutical developers are now working toward.

For more on early MS signs, the 2024 McDonald diagnostic criteria, and the broader MS treatment landscape, see our related guide: “Who Was I to Know?” — Early Signs of Multiple Sclerosis and Why Early Diagnosis Matters More Than Ever.

EBV and cancer

EBV was the first human virus ever identified as cancer-causing, and its role in oncology has been well-established for decades. EBV is associated with approximately 200,000 new cancer cases globally each year, across several distinct cancer types:

• Burkitt lymphoma — the cancer in which EBV was first discovered, particularly common in parts of Africa where malaria is endemic
• Hodgkin lymphoma — EBV is found in a significant subset of cases
• Non-Hodgkin lymphomas, particularly in immunocompromised patients
• Nasopharyngeal carcinoma — strongly associated with EBV in certain geographic regions, especially Southeast Asia
• Gastric (stomach) cancer — roughly 10% of cases worldwide are EBV-associated
• Post-transplant lymphoproliferative disease — a complication in organ transplant recipients whose immune systems are suppressed

Most people infected with EBV will never develop an EBV-associated cancer. Additional factors — genetic predisposition, environmental exposures, immune status, co-infections — appear to determine which patients progress from benign latent infection to malignancy. Understanding these factors is an active area of research.

EBV reactivation, long COVID, and chronic fatigue

One of the most clinically important developments of the past few years has been the recognition that EBV reactivation plays a significant role in post-viral and chronic fatigue conditions. When patients develop long COVID — the constellation of persistent symptoms that can follow SARS-CoV-2 infection — many of them show signs of reactivated latent EBV infection.

Research published in 2025 has detailed several proposed mechanisms for this phenomenon. SARS-CoV-2 infection appears to cause immune dysregulation that allows dormant EBV to reawaken. Once reactivated, EBV can contribute to ongoing inflammation, mitochondrial dysfunction, and the classic post-viral symptom cluster: crushing fatigue, cognitive dysfunction (“brain fog”), exercise intolerance, and neuropsychiatric symptoms.

The overlap between long COVID and myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) has drawn intense research attention. ME/CFS has long been associated with post-viral syndromes, particularly following mononucleosis. A 2023 study in the Journal of Translational Medicine proposed that EBV reactivation may be a common thread linking both conditions, through a process that creates a form of acquired immunodeficiency in susceptible individuals.

This research has real implications for patients. Many people experiencing persistent fatigue after a viral illness have historically been told their symptoms are stress-related or psychological. The growing body of evidence on EBV reactivation provides a biological explanation — and increasing motivation to study these conditions seriously.

EBV and other autoimmune conditions

Beyond MS, EBV has been implicated in the development or triggering of several other autoimmune conditions, including:

• Systemic lupus erythematosus (lupus)
• Rheumatoid arthritis
• Sjögren’s syndrome
• Inflammatory bowel disease, particularly ulcerative colitis
• Hashimoto’s thyroiditis and Graves’ disease
• Type 1 diabetes — though evidence is more mixed

The mechanisms appear to overlap with what has been identified in MS: molecular mimicry, dysregulation of B cell immunity, and chronic low-level viral activity that keeps the immune system in an activated state. Not everyone with these conditions has evidence of active EBV involvement, and EBV is only one of several factors that contribute to autoimmune disease risk. But it is a thread that runs through an increasing number of diagnoses — and understanding that thread may reshape how we approach autoimmunity in the coming decade.

The race to develop an EBV vaccine

Despite being one of the most common human viruses in the world — and despite its links to mono, cancer, and autoimmune disease — there is currently no approved vaccine for Epstein-Barr virus. That may be about to change. Several candidate vaccines are now in clinical trials.

Moderna’s mRNA vaccines

Moderna — the company behind one of the first approved COVID-19 vaccines — is leading the effort with multiple candidates based on its mRNA platform technology. Two vaccines are currently in trials:

• mRNA-1189 was the first EBV mRNA vaccine candidate to enter human trials. A Phase 1 study (the Eclipse trial, NCT05164049) has been evaluating its safety and immune response in healthy participants aged 12 to 30.
• mRNA-1195 is a next-generation candidate designed to target additional viral proteins. It is being evaluated in a Phase 1 dose-ranging study (NCT05831111) in healthy adults.

Most significantly, in November 2025 Moderna launched a Phase 2 trial (NCT06735248) specifically testing an EBV vaccine in patients with early multiple sclerosis. The study is enrolling 180 adults aged 18 to 55 who have relapsing MS diagnosed within the past two years and who are EBV-seropositive. Participants receive either a high or low dose of the vaccine or placebo over a six-month period, and are followed for about 2.5 years. The central question: can vaccinating against EBV slow the progression of MS?

The NIH nanoparticle vaccine

The National Institutes of Health has developed a separate candidate vaccine using a different approach. The NIH EBV gp350-Ferritin nanoparticle vaccine uses a nanoparticle platform to present a specific EBV protein (gp350) to the immune system, paired with a saponin-based Matrix-M adjuvant. This vaccine entered Phase 1 trials (NCT05683834) at the NIH Clinical Center in Bethesda, Maryland.

Why this matters

If any of these vaccines proves safe and effective at preventing EBV infection — or at controlling it in already-infected patients — the downstream implications are enormous. A successful EBV vaccine could potentially:

• Prevent infectious mononucleosis in adolescents
• Reduce the incidence of EBV-associated cancers
• Prevent or delay the onset of multiple sclerosis in at-risk individuals
• Reduce risk for certain autoimmune diseases
• Potentially change treatment for patients with existing MS

This is among the most important areas of vaccine research currently underway. Results from the Phase 2 MS trial are expected over the next several years.

What patients can do now

Given how common EBV is and how recently much of this research has emerged, many patients understandably wonder what to do with this information. A few practical considerations:

If you’ve had mono in the past. The vast majority of people who have had mono will never develop MS, an EBV-associated cancer, or chronic fatigue syndrome. Having had mono is not, on its own, cause for alarm. However, if you develop persistent fatigue, new neurological symptoms, or ongoing unexplained illness, it is reasonable to mention your history of mono to your doctor — especially now that the research landscape has evolved.

If you’re experiencing persistent fatigue after a viral illness. Long COVID, post-mono fatigue, and ME/CFS are real and increasingly recognized conditions. If you have been dismissed in the past, the current science supports taking these symptoms seriously. Ask your doctor about EBV-related testing if appropriate, and consider evaluation by a specialist familiar with post-viral syndromes.

If you have MS or a family history of MS. Current research on the EBV-MS connection is informing treatment development and may eventually inform prevention for family members at higher genetic risk. For patients currently living with MS, standard disease-modifying therapies remain the foundation of care. The EBV-targeted approaches in development are being studied as potential additions to — not replacements for — existing treatments.

If you are interested in clinical trials. The ClinicalTrials.gov database maintains current listings of EBV vaccine studies and related research. Participation is voluntary, and trials have specific eligibility criteria.

For everyone. Basic immune health matters. Sleep, stress management, nutrition, and regular exercise all support the immune system’s ability to keep latent viruses under control. This is not a replacement for medical care, but it is a foundation that benefits anyone carrying a latent herpesvirus — which, statistically, is almost everyone.

Key takeaways

• Epstein-Barr virus infects approximately 95% of adults worldwide. Most infections occur in childhood or adolescence and are mild or silent.
• EBV was the first human virus ever shown to cause cancer. It is associated with roughly 200,000 new cancer cases globally each year.
• Landmark research in 2022 established EBV as very likely a cause of multiple sclerosis, with subsequent studies revealing the biological mechanisms.
• EBV reactivation appears to play a significant role in long COVID and myalgic encephalomyelitis / chronic fatigue syndrome (ME/CFS).
• EBV is implicated in several other autoimmune conditions, including lupus, rheumatoid arthritis, and Sjögren’s syndrome.
• Multiple EBV vaccine candidates are now in clinical trials, including Moderna’s mRNA platform and NIH’s nanoparticle vaccine. A Phase 2 trial specifically in MS patients launched in November 2025.
• If you have persistent symptoms after a viral illness, take them seriously. The science is increasingly supportive of post-viral conditions as legitimate medical entities.
• The EBV research landscape is moving rapidly. What we know today is substantially different from what was understood even five years ago — and the pace of discovery is accelerating.

Sources and references

1. Bjornevik K, Cortese M, Healy BC, et al. Longitudinal analysis reveals high prevalence of Epstein-Barr virus associated with multiple sclerosis. Science. 2022;375(6578):296-301.
2. Lanz TV, Brewer RC, Ho PP, et al. Clonally expanded B cells in multiple sclerosis bind EBV EBNA1 and GlialCAM. Nature. 2022;603(7900):321-327.
3. Sabatino JJ, et al. Antigen specificity of clonally enriched CD8+ T cells in multiple sclerosis. Nature Immunology. 2026;27(3):490-502. UCSF coverage.
4. Nguyen JT, et al. EBV infection and HLA-DR15 jointly drive multiple sclerosis by myelin peptide presentation. Cell. 2026;189(2):569-584.
5. Soldan SS, Lieberman PM. Epstein-Barr virus and multiple sclerosis. Nature Reviews Microbiology. 2023;21(1):51-64.
6. National Institutes of Health. NIH launches clinical trial of Epstein-Barr virus vaccine. Available at: nih.gov
7. ClinicalTrials.gov. Moderna mRNA-1195 Phase 1 trial (NCT05831111). Available at: clinicaltrials.gov
8. ClinicalTrials.gov. Moderna Phase 2 EBV vaccine trial in early MS (NCT06735248).
9. ClinicalTrials.gov. NIH gp350-Ferritin EBV vaccine Phase 1/2 (NCT05683834). Available at: clinicaltrials.gov
10. Ruiz-Pablos M, Paiva B, Zabaleta A. Epstein-Barr virus-acquired immunodeficiency in myalgic encephalomyelitis—Is it present in long COVID? J Transl Med. 2023;21:633.
11. Ling J, Li J. What could cause the reactivation of Epstein-Barr virus in individuals with long COVID. Emerg Microbes Infect. 2025.
12. Centers for Disease Control and Prevention. About Epstein-Barr Virus (EBV). Available at: cdc.gov
13. National Multiple Sclerosis Society. Available at: nationalmssociety.org