Multiple Sclerosis (MS), a debilitating autoimmune disease, may in fact be caused by a virus, suggests a new study published in Science by Harvard Medical School Researchers.

The researchers tested a cohort of more than 10 million young adults on active duty in the US military between 1993 and 2013. During this 20-year timeframe, 955 individuals were diagnosed with MS over the course of their period of service. The researchers found that the risk of MS increased 32-fold after infection with the Epstein-Barr virus, known as EBV for short.

MS is a chronic inflammatory demyelinating disease of the central nervous system. The chronic inflammation occurs when the immune system mistakenly attacks the protective sheath (myelin) that covers nerve fibers, causing communication problems between your brain and the rest of your body. According to the Mayo Clinic, the disease can eventually cause permanent damage or deterioration of the nerves. Other symptoms include vision problems, slurred speech, fatigue, dizziness, tingling or pain in parts of the body, and bowel, bladder, and sexual dysfunction.

Multiple Sclerosis and the Epstein-Barr Virus

Although the exact cause of multiple sclerosis is unknown, it has long been hypothesized that the demyelination in the brain and spinal course is triggered by a viral infection. This particular study found that serum levels of neurofilament light chain, a biomarker of neuroaxonal degeneration, increased only after EBV seroconversion, suggesting that EBV is a leading cause of MS. However, the risk of MS was not increased after infection with other viruses, such as the cytomegalovirus (CMV); the researchers had also compared samples to CMV positivity as a negative control group, and found that CMV positivity was actually associated with a lower risk of MS.

“The key finding is that MS is a complication of infection with EBV,” said Alberto Ascherio, a professor of epidemiology and nutrition at Harvard’s T.H. Chan School of Public Health. Commenting on the size and longevity of the study, Ascherio said: “There is no comparable population in the world.”

Stanford University researchers believe that molecular mimicry may be the culprit behind why those infected with Epstein-Barr have a higher risk of developing MS. Molecular mimicry occurs when immune cells targeting EBV accidentally attack myelin, due to the molecular similarities between the virus and this tissue. A 2018 study identified EBV-infected B cells in the brains of MS patients, lending support to the molecular mimicry theory.

Multiple Sclerosis: Vitamin D Deficiency and Genetic Factors

It’s unlikely that EBV is the sole reason behind the development of MS, however. The study suggests that EBV seropositivity is necessary to develop MS, but it isn’t sufficient – otherwise, 95% of the world’s population would have MS, since the virus is prevalent worldwide. According to the UK-based Multiple Sclerosis Trust, an estimated 2.5 million people worldwide have multiple sclerosis. So why do only some people develop MS and not others?

Another theory about the development of MS is vitamin D deficiency. Vitamin D, also known as the sunshine vitamin, may be a protective compound against the development of MS; it has been found, for instance, that the distribution of MS around the world is uneven; generally, the prevalence of the disease increases as you travel further north or south from the equator. The parts of Asia, Africa and America that lie on the equator have extremely low levels of MS, while Canada and Scotland have particularly high rates. This suggests that vitamin D, particularly from the sun, is important in preventing MS, possibly due to its anti-inflammatory properties.

Other studies have shown that certain ethnic groups have a markedly lower prevalence of MS, despite living in places where the disease is more common. For example, the Sami or Lapps of northern Scandinavia, the Inuits of Canada and Greenland (Denmark), and the Maoris of New Zealand exhibit very low rates of MS, despite living in some of the northernmost and southernmost climates in the world.

Multiple Sclerosis and Diet

Another theory that has evolved is the relationship between Multiple Sclerosis and one’s diet. As noted above, many northernmost communities do not get sufficient vitamin D from the sun, due to their local climate. However, they make up for this by consuming a vitamin D-rich diet; for example, fish and marine mammals like seal and whale. These foods are also rich in healthy omega-3 fatty acids, which are also known to have anti-inflammatory properties and may help other autoimmune conditions beyond MS, like rheumatoid arthritis, Crohn’s disease, ulcerative colitis, and systemic lupus erythematosus.

Although considered controversial to some, Dr. Terry Wahls, who has multiple sclerosis herself, developed a dietary approach to treating autoimmune conditions with paleo principals, which she calls the Wahls Protocol.

New Ways to Treat MS

Ascherio, for his part, believes that his team’s groundbreaking research on the connection between viruses like Epstein-Barr and MS could pioneer the development of new multiple sclerosis treatments. For example, immunosuppressive therapies that deplete B cells infected by EBV.

There is also renewed interest in developing vaccines and antivirals against EBV with the objective of eradicating MS. While antivirals targeting EBV don’t yet exist, Ascherio says their development is realistic: “Once you establish the causal connection, I think it’s a question of providing sufficient rational for research on antivirals, specifically for EBV, that could help people with MS [around] the world,” he concluded.