Mononucleosis & Multiple Sclerosis: Shocking Link Revealed

A new study has strengthened the link between infectious mononucleosis (mono) and an increased risk of developing multiple sclerosis (MS). Researchers analyzing over two decades of health records found that individuals who contracted the Epstein-Barr virus (EBV) as teenagers or adults – resulting in a clinical case of mono – were three times more likely to develop MS later in life compared to those who did not contract the virus.

The study, published on April 1, 2026, in Neurology Open Access, does not prove that mono causes MS, but demonstrates a significant association between the two conditions. While MS is a relatively rare disease, these findings suggest that future vaccines targeting EBV could potentially reduce the global burden of MS.

Threefold Risk Increase

After adjusting for factors such as smoking, race, and underlying health conditions like diabetes and depression, the study revealed a 300% increase in MS risk for those with a history of mono. Specifically, 0.17% of individuals in the mono group (8 out of 4,721) developed MS, equating to 2.25 cases per 10,000 person-years. In contrast, only 0.07% of the control group (10 out of 14,163) developed MS, representing 0.77 cases per 10,000 person-years.

Age of Infection Matters

The Epstein-Barr virus is extremely common, infecting most people at some point in their lives. However, the study highlights that the timing of infection is crucial. When EBV is contracted later in life – during adolescence or adulthood – it often manifests as mono, which appears to be the specific event that escalates the risk of developing MS. Infection during childhood is less strongly linked to the increased risk.

EBV and Multiple Sclerosis: A Growing Body of Evidence

Research suggesting a link between EBV and MS has been ongoing for decades. Recent studies have further solidified this connection. A longitudinal analysis has revealed a high prevalence of Epstein-Barr virus in individuals with multiple sclerosis. The findings reinforce the idea that there isn’t a clear dividing line between infectious and chronic diseases.

Jennifer Beam Dowd, Ph.D., writing in Psychology Today, notes that only a small fraction of people infected with EBV ultimately develop MS, indicating that other factors likely play a role in the disease’s development.

“Only a small fraction of people infected with EBV get MS, meaning EBV interacts with other factors.”

Jennifer Beam Dowd, Ph.D., Psychology Today

Vaccine Development

The study was supported by ModernaTX, Inc., which is currently developing vaccines specifically designed to target EBV-associated conditions, including MS. The research underscores the potential for such vaccines to significantly reduce the incidence of MS globally.

The Epstein-Barr virus is a herpesvirus that remains dormant in the body for life after infection, with potential flare-ups during periods of immunosuppression. Mono, often referred to as the “kissing disease,” is primarily spread through saliva and is common among teenagers and young adults.

While the study establishes a strong association, further research is needed to fully understand the mechanisms by which EBV may contribute to the development of MS and to determine the effectiveness of EBV vaccines in preventing the disease.