Teenage Mono Linked to Tripled Risk of Multiple Sclerosis Later in Life, Study Finds

A bout of mononucleosis contracted in adolescence may do more than just sideline a high schooler for weeks—it could set the stage for a far more serious health crisis decades later. In a sweeping new study published Wednesday in the journal Neurology Open Access, researchers at the Mayo Clinic and collaborating institutions have uncovered a striking correlation: people diagnosed with infectious mononucleosis, often caused by the Epstein-Barr virus (EBV), are three times more likely to develop multiple sclerosis (MS) later in life compared to those who never had mono. The findings, derived from an analysis of nearly 19,000 medical records, add substantial weight to the growing scientific consensus that EBV—one of the most common human viruses—plays a pivotal role in triggering the debilitating autoimmune disease.

Why This Study Matters: Unpacking the Mono-Multiple Sclerosis Connection

Multiple sclerosis is a chronic, often progressive disease of the central nervous system that disrupts communication between the brain and body. Symptoms range from muscle weakness and vision problems to severe fatigue and cognitive decline, with an average age of onset around 20 to 40 years. Despite decades of research, the exact cause of MS remains elusive. However, mounting evidence—including this latest study—points to EBV as a central suspect. Roughly 95% of adults worldwide are infected with EBV by age 40, but only about 1% go on to develop MS. This disparity suggests that EBV alone isn’t sufficient to trigger the disease; rather, it may act as a catalyst in individuals with genetic or environmental predispositions.

What Is Mononucleosis and How Is It Connected to EBV?

Infectious mononucleosis, commonly known as mono or the "kissing disease," is an illness most often caused by EBV. The virus spreads through saliva, making close contact—such as kissing, sharing utensils, or coughing—its primary transmission route. While EBV infections in young children are often mild or asymptomatic, adolescents and young adults are more likely to develop classic mono symptoms approximately four to six weeks after exposure. These include extreme fatigue, fever, swollen lymph nodes, a severe sore throat, and sometimes a measles-like rash. Recovery typically takes two to four weeks, but about 10% of patients experience prolonged fatigue lasting months.

Decades of Research: From Correlation to Causation in MS and EBV

The link between EBV and MS has been studied for over a decade. Landmark research published in 2022 in Science definitively established EBV as the leading cause of MS, finding that the risk of developing the disease increases by more than 30-fold after EBV infection. This groundbreaking study used antibody tests to confirm EBV status in military personnel, providing strong evidence that EBV precedes MS onset by several years. Earlier work had shown that people with MS were more likely to have antibodies against EBV, but those studies were often limited by self-reported mono cases or incomplete medical histories. The new Mayo Clinic study addresses these limitations by focusing exclusively on patients with laboratory-confirmed EBV-positive mono, offering a more precise measure of risk.

How the Study Was Conducted: A Deep Dive into the Data

To assess the long-term risk of MS following mono, researchers conducted a retrospective cohort study using the medical records of 18,884 individuals. The study group consisted of 4,721 patients diagnosed with mono confirmed by a positive EBV test, while the control group included 14,163 individuals without mono, matched for age, sex, and other demographic factors. Participants were tracked for a median of six to eight years. During this period, MS diagnoses were recorded using standard clinical criteria, including magnetic resonance imaging (MRI) and cerebrospinal fluid analysis.

The Findings: A Clear, Quantifiable Risk

Even after adjusting for confounding factors such as smoking, depression, and socioeconomic status, the data revealed a stark disparity. Among those with a history of EBV-positive mono, 0.25% developed MS, compared to just 0.08% in the control group. This translated to a 3.25-fold increased risk—over three times higher. While the absolute risk remains low, the relative risk is substantial and statistically significant. Importantly, the study did not find an elevated risk of MS in people who had mono not caused by EBV, reinforcing the specific role of EBV in the disease process.

Limitations and What They Mean for Future Research

Despite its strengths, the study has limitations. As a retrospective analysis, it relies on existing medical records, which may not capture all relevant health information. Additionally, the follow-up period of six to eight years is relatively short compared to the decades-long latency period often seen in MS. The authors acknowledge that more research is needed to understand how EBV triggers MS and why only a fraction of infected individuals are affected. Genetic factors, such as specific HLA gene variants, and environmental triggers like vitamin D deficiency or smoking may interact with EBV to increase MS risk.

The Bigger Picture: Why EBV Vaccines Are Essential

The study’s authors emphasize that their findings underscore an urgent need for effective EBV vaccines—not just to prevent mono, but to potentially reduce the risk of MS. Currently, there is no vaccine approved for EBV in the United States, though several candidates are in late-stage clinical trials. The most advanced, developed by Moderna, uses mRNA technology similar to its COVID-19 vaccine and has shown promising results in Phase 2 trials. If successful, such a vaccine could not only alleviate the immediate burden of mono but also address a major risk factor for MS.

“Together with previous studies, our findings highlight the importance of continued efforts to develop preventive strategies against EBV-positive infectious mononucleosis. A vaccine could be a game-changer not only for reducing acute illness but also for potentially lowering the long-term risk of multiple sclerosis.”

Public health experts agree. Dr. Alberto Ascherio, a professor of epidemiology and nutrition at Harvard T.H. Chan School of Public Health and a co-author of the 2022 Science study, stated in a recent interview, “The evidence is now overwhelming that EBV is a necessary cause of MS. While not everyone with EBV will develop MS, preventing EBV infection could eliminate a large proportion of MS cases.”

Key Takeaways: What You Need to Know

• People who had infectious mononucleosis caused by the Epstein-Barr virus (EBV) in their teens or early adulthood are three times more likely to develop multiple sclerosis (MS) later in life, according to a Mayo Clinic-led study of 18,884 individuals.
• EBV is nearly ubiquitous, infecting 95% of adults by age 40, but only about 1% of those infected develop MS, suggesting that genetic or environmental factors interact with the virus to trigger the disease.
• The study used confirmed EBV-positive mono cases, avoiding the inconsistencies of earlier research that relied on self-reported illness, and tracked participants for six to eight years.
• While the absolute risk of developing MS after mono remains low, the relative risk increase is significant and supports the urgent development of EBV vaccines.
• Public health experts emphasize that preventing EBV infection could substantially reduce MS cases, given the virus’s role as a leading cause.

Frequently Asked Questions about Mono, EBV, and Multiple Sclerosis