What Is Epstein-Barr Virus and Why Does It Cause Disease?
Epstein-Barr virus infects roughly 95% of adults worldwide, hides in immune cells for life, and is linked to multiple sclerosis, several cancers, and other serious conditions. Here is how it works and why scientists are racing to stop it.
The World's Most Common Virus
Epstein-Barr virus (EBV) is one of the most successful human pathogens ever identified. Discovered in 1964 by Sir Michael Anthony Epstein and Yvonne Barr, this member of the herpesvirus family infects an estimated 95% of all adults worldwide, typically during childhood or early adulthood. Most people never realize they carry it — yet the virus stays with them for life, silently lodged inside immune cells, capable of reactivating and potentially triggering serious disease.
How the Virus Spreads and Takes Hold
EBV spreads primarily through saliva, which is why infectious mononucleosis — the most well-known illness it causes — earned the nickname "the kissing disease." Sharing drinks, utensils, or toothbrushes can also transmit the virus. Less commonly, EBV spreads through blood transfusions, organ transplants, or sexual contact.
Once inside the body, EBV targets the epithelial cells of the throat, particularly the tonsils and surrounding tissue known as Waldeyer's ring. From there, it crosses into B cells — a critical type of white blood cell responsible for producing antibodies. The virus uses a surface protein called gp350 to latch onto a receptor (CD21) on the B cell, then deploys additional proteins including gp42 to fuse with and enter the cell.
What happens next is what makes EBV so persistent. Rather than simply destroying its host cell, the virus reprograms the B cell to proliferate, then gradually silences most of its own genes. Eventually, infected cells become memory B cells — long-lived immune cells that express little or no viral protein, making them nearly invisible to the immune system. This is latent infection, and it lasts a lifetime.
From Mono to Multiple Sclerosis and Cancer
In teenagers and young adults, a first encounter with EBV often triggers infectious mononucleosis — marked by severe fatigue, sore throat, swollen lymph nodes, and fever that can last weeks. In younger children, the initial infection is usually mild or asymptomatic.
But EBV's most consequential effects may emerge years or decades later. The virus is now classified as a Group 1 carcinogen by the International Agency for Research on Cancer. It is causally linked to nasopharyngeal carcinoma, Burkitt lymphoma, Hodgkin lymphoma, and certain stomach cancers. Globally, EBV-associated cancers account for an estimated 1.5% to 2% of all human malignancies — roughly 200,000 new cases per year.
Perhaps the most dramatic recent finding links EBV to multiple sclerosis. A landmark 2022 study published in Science, tracking over 10 million U.S. military personnel, found that EBV infection increased the risk of developing MS by more than 32-fold. The risk among those never infected was negligible. Researchers believe the virus may trigger MS through molecular mimicry — viral proteins that resemble proteins in the brain's myelin sheath, causing the immune system to attack its own nervous tissue.
Why There Is No Vaccine — Yet
Despite infecting virtually all humans, EBV has no approved vaccine or antiviral treatment. The virus's ability to hide inside memory B cells, express minimal proteins during latency, and reactivate unpredictably has made it an exceptionally difficult target.
That may be changing. In February 2026, researchers at Fred Hutchinson Cancer Center developed powerful antibodies targeting the gp350 and gp42 proteins, with one antibody completely blocking infection in laboratory models. Meanwhile, the U.S. National Institutes of Health launched a Phase 1 clinical trial of a ferritin nanoparticle vaccine designed to prevent EBV infection entirely. Moderna is testing an mRNA-based vaccine (mRNA-1195) in a Phase 2 trial specifically aimed at reducing MS disease activity, with results expected by 2029.
Why It Matters
EBV sits at the intersection of virology, oncology, and autoimmune disease in a way that few other pathogens do. A successful vaccine would not only prevent mononucleosis but could potentially prevent multiple sclerosis and reduce tens of thousands of cancer cases annually. For a virus that hides inside nearly every human on Earth, even partial success would represent one of the most significant public health advances in decades.
