Researchers at Harvard T.H. Chan School of Public Health dropped a public health bombshell this week in the journal Science: multiple sclerosis (MS) is likely caused by infection with Epstein-Barr virus, also known as EBV.
MS is a chronic inflammatory disease of the central nervous system. The disease involves an immune response that attacks the nerves themselves, leading to progressive neurological problems. About a million people in the United States have MS, and millions more worldwide.
The link between EBV and MS has been suspected for a long time, and now for the first time, we have solid evidence of a causal link. Researchers tracked 10 million military recruits for more than 20 years. They used stored samples from old HIV tests to discover whether the recruits had already had EBV when they enrolled in the service. By careful data collection on recruits who later developed MS, researchers were able to learn that MS risk was 32 times higher after infection with EBV. On average, MS onset was 7.5 years after the EBV infection. MS risk was not explained by any other factors, including infection with another common virus that has a similar transmission route.
You may know EBV best as “infectious mono.” In young children, EBV infection can be so mild that no one even notices it, or it can be indistinguishable from any other childhood bug.
Symptoms tend to be worse and last longer in older kids and adults. They include extreme fatigue, fever, sore throat, body aches, headache, swollen lymph nodes, and a rash. The fatigue, especially, can last for weeks or even months.
EBV is spread mainly by saliva, which has led to it being called colloquially the “kissing disease.” However, most people get it as children by sharing drinks and eating utensils. Outbreaks sometimes happen in childcare settings, since it spreads easily when toddlers… lick stuff.
EBV is a virus in the herpes family. Other herpesviruses include herpes simplex virus-1 (which causes cold sores) and varicella-zoster (which causes chickenpox and shingles). EBV and other herpes viruses cause latent infections. That means after the acute infection, the virus goes dormant, hiding for years or decades inside our cells.
EBV infects epithelial cells (like your mouth and stomach lining) and the B cells of the immune system. While it is active, it uses your cells to make lots of infectious copies of itself. But when it goes latent, it just hides out, waiting for an opportune moment to reactivate and start replicating again. This often happens in times of stress when the immune system is strained.
EBV is extremely common–in fact, about half of kids have it by age 5, and 95 in 100 adults in the United States will get it in their lifetimes.
However, MS is very rare. It’s not known why EBV infection leads to the development of MS in an unlucky few, but these researchers suggest that it could be due to a genetic predisposition triggered by the infection. EBV has also been linked to other serious immune-mediated diseases such as lupus, rheumatoid arthritis, Burkitt’s lymphoma, Hodgkin’s lymphoma, and several other types of cancer. And here’s an odd factoid: EBV infection has been linked to terrible mosquito bite allergies.
Even with many unknowns still in the mix, this is nonetheless a major breakthrough for MS prevention and treatment. The current treatment for MS involves suppressing B cells, but the Harvard team says their findings could mean new treatment options, like antivirals.
There is currently no vaccine for EBV, but it has been a goal for years. This new evidence will help prioritize research in the ongoing development of a vaccine. Just before the MS news broke, Moderna gave the first humans their in-development EBV vaccine in a Phase I clinical trial.
CDC – Epstein-Barr Virus and Infectious Mononucleosis
National MS Society – Landmark Study Estimates Nearly 1 Million in the U.S. Have Multiple Sclerosis
Harvard – Epstein-Barr virus may be leading cause of multiple sclerosis
Clinical Trials Arena – Moderna doses first subject in Phase I EBV vaccine trial
