Epstein-Barr Virus Linked to Multiple Sclerosis Relapses, New Study Suggests

A common virus present in nearly 90% of Americans, the Epstein-Barr virus (EBV), has been linked to an increased risk of multiple sclerosis (MS) relapses, according to a new study.

The research, published in Nature Medicine, found that active EBV particles may increase in the bloodstream before an MS flare-up, potentially triggering symptoms such as muscle weakness, vision loss, numbness, and fatigue.

EBV, a member of the herpes virus family, is widely known for causing infectious mononucleosis, commonly referred to as mono or the 'kissing disease.' Once contracted, the virus typically remains dormant in the body but can reactivate, particularly under stress or with a weakened immune system. It is estimated that approximately 300 million Americans have been exposed to EBV in their lifetime.

Previous studies have indicated that EBV infection could more than triple the risk of developing MS. MS affects about one million Americans, characterized by the immune system attacking the protective covering of nerves in the brain and spinal cord, disrupting communication signals between the brain and the body.

In the recent study, researchers analyzed blood samples from 114 individuals with MS and 21 healthy control subjects. They employed molecular techniques, including single-cell RNA sequencing, to examine changes in immune cells. This method allows for the analysis of thousands of individual blood cells to identify those undergoing the most significant alterations.

The study revealed that B cells, a type of white blood cell capable of harboring EBV, showed the most pronounced changes. These cells appeared to be transitioning from a normal state to an activated one, suggesting an immune response was being stimulated. This activation was observed to increase prior to an MS relapse.

Furthermore, researchers identified EBV-related signals that were associated with the activation of genes known to increase susceptibility to MS. This pattern was not observed in individuals in remission or in healthy individuals.

While the study does not offer methods for preventing MS relapses, it opens possibilities for new therapeutic strategies targeting EBV to alleviate debilitating symptoms. Dr. Tanuja Chitnis, the senior author, stated in a press release that these findings present a new pathway for targeted therapies. Current MS treatments often involve broad suppression of the immune system, but the study suggests a more precise approach could be developed by targeting EBV or the specific immune cells involved in relapses.

The exact cause of MS remains elusive, but scientists believe a combination of genetic predisposition, environmental factors, and viral infections, particularly EBV, plays a significant role.

Mono is highly prevalent, especially among adolescents and young adults. Although a vast majority of people carry EBV, only a fraction develop symptomatic mono upon initial exposure. The virus is primarily spread through saliva, and transmission during adolescence often occurs via kissing.

Symptoms of mono typically include extreme fatigue, severe sore throat, fever, and swollen lymph nodes. Some individuals also experience swollen tonsils, headaches, body aches, and an enlarged spleen.

Another study published in Neurology Open Access in April 2026 tracked nearly 19,000 individuals and found that children and young adults with lab-confirmed EBV and symptomatic mono were significantly more likely to develop MS later in life compared to those without a history of EBV-positive mono. These findings emphasize the need for preventive strategies, potentially including an EBV vaccine, to mitigate the long-term impact of MS.