A virus that infects the vast majority of people at some point in their lives, usually with mild or unnoticed symptoms, has emerged as the leading suspected cause of multiple sclerosis, a disabling disease of the central nervous system that can strike years or even decades later. The link between the Epstein-Barr virus and multiple sclerosis had been suspected for years, but a landmark analysis of millions of young adults transformed a plausible association into what many researchers now regard as the strongest evidence yet that the common infection is a necessary precursor to the disease. The finding does not mean that catching the virus guarantees illness, since nearly everyone is infected while only a tiny fraction develop multiple sclerosis, but it reframes how scientists think about preventing a condition that has long defied explanation.
The military cohort that changed the picture
The pivotal evidence came from a study tracking more than 10 million young adults on active duty in the U.S. military, whose blood samples were collected and stored over roughly two decades. Among them, 955 were diagnosed with multiple sclerosis during their service, giving researchers a rare opportunity to examine whether infection preceded disease. Published in the journal Science, the analysis of Epstein-Barr virus and multiple sclerosis found that the risk of developing the disease rose 32-fold after infection with the virus, while infection with other viruses produced no comparable increase. Because the stored samples captured each person’s infection status over time, the researchers could establish that the virus arrived first and the disease followed, a sequence that is difficult to prove in most studies.
What the timing revealed
The temporal pattern proved especially telling. Nearly all of the individuals who went on to develop multiple sclerosis had become infected with the Epstein-Barr virus before any clinical signs of the disease appeared, with a median lag of about 7.5 years between infection and onset. Researchers also tracked a marker of nerve damage called neurofilament light chain, a protein that leaks into the blood when nerve fibers are injured, and found that its levels rose only after infection with the virus. That ordering, described in the study record indexed on the National Library of Medicine’s PubMed database, strengthened the case that the virus is not merely associated with the disease but sits upstream of the biological damage that defines it.
How Epstein-Barr virus behaves in the body
The Epstein-Barr virus is one of the most common human viruses, best known as a cause of infectious mononucleosis, and it spreads chiefly through saliva. As the Centers for Disease Control and Prevention explains in its overview of the Epstein-Barr virus, most people are infected at some point, often in childhood when the infection produces few or no symptoms, and the virus then persists in a latent state within immune cells for the rest of a person’s life. This lifelong presence is central to theories about how the virus might trigger multiple sclerosis, because a dormant virus can periodically reactivate and continually engage the immune system. The near-universal nature of the infection is also what makes the disease connection so puzzling: if almost everyone carries the virus, some additional factor must determine why only a small number develop multiple sclerosis.
Why multiple sclerosis is so damaging
Multiple sclerosis occurs when the immune system attacks the protective myelin sheath surrounding nerve fibers in the brain and spinal cord, disrupting the signals that travel through them. The National Institute of Neurological Disorders and Stroke, in its description of multiple sclerosis, notes that symptoms can include vision problems, muscle weakness, difficulty with coordination and balance, numbness, and cognitive changes, and that the disease often follows a relapsing course before progressing. One leading hypothesis for the viral link is molecular mimicry, in which immune cells generated to fight the virus mistakenly recognize a similar-looking protein in nerve tissue and attack the body’s own myelin, though the precise mechanism remains under active investigation.
The prospect of prevention
If the Epstein-Barr virus is indeed a necessary cause of multiple sclerosis, then blocking or neutralizing the infection could, in principle, prevent the disease, an idea that has energized efforts to develop a vaccine against the virus and to pursue antiviral strategies aimed at its latent form. Coverage of the research, including reporting compiled by outlets such as ScienceDaily, has highlighted how the findings shift the target of prevention from the immune system’s downstream misfires toward the infection that appears to set the process in motion. Scientists caution that a vaccine or antiviral capable of preventing multiple sclerosis remains years away and that the disease’s full causal chain is not yet mapped. But identifying a single, widespread and potentially preventable trigger has given the field a concrete objective it lacked for decades.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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