Which infectious agent is listed as a potential risk factor for MS?

• A. Varicella Zoster virus.
• B. Epstein-Barr virus.
• C. Influenza virus.
• D. HIV.

Answer: (B)

Epstein-Barr virus is the infectious agent most consistently linked to a higher risk of developing MS. Large studies show that having EBV infection, especially when it manifests as infectious mononucleosis in adolescence or young adulthood, is associated with a significantly increased chance of later MS. In fact, most people with MS are EBV-seropositive, and higher EBV antibody levels tend to correlate with greater risk. Mechanistically, EBV can persist in B cells and drive immune processes that may become autoimmune against myelin, possibly through molecular mimicry or abnormal B-cell activity. Other common viruses like Varicella Zoster, influenza, or HIV do not show the same robust, consistent association with MS risk in the data.