Large Israeli study finds distinct relationships between common herpesviruses and multiple sclerosis risk

Viral exposures are long-suspected environmental contributors to multiple sclerosis (MS). Epstein-Barr virus (EBV) has been repeatedly linked to MS risk, but the roles of other common herpesviruses—herpes simplex virus (HSV) and cytomegalovirus (CMV)—have been inconsistent across prior studies. This large-scale case-control analysis used clinical records to compare the associations of prior EBV, HSV, and CMV infections with later MS diagnoses.

• EBV: Prior infection was the most common (present in about 30.8% of the sample) and was associated with a 46% higher chance of a subsequent MS diagnosis after adjustment for potential confounders.

• CMV: Initial analyses found a 36% lower MS risk associated with prior CMV infection, but this result was not statistically significant in the full sample. When the control group was restricted to individuals who had a negative blood CMV test (and no positive tests on record), CMV infection was significantly associated with a 49% lower chance of later MS. This association remained significant in sensitivity analyses that used a one-year washout and adjusted for EBV status.

• HSV: Prior HSV infection showed a 19% higher odds of MS, but the association did not reach statistical significance.

This is an observational case-control analysis of routine clinical and laboratory records. It establishes associations, not causation. The differential methods used to identify prior infection across viruses (antibody tests for EBV and CMV versus diagnostic coding for HSV) can affect detection and comparisons. The study improves on smaller prior studies by sample size, matched controls, adjustment for key confounders, and sensitivity checks, but residual biases and testing-pattern differences may remain.

If you follow MS research, this study adds weight to EBV's role as a major infection-related risk marker and suggests CMV might correlate with reduced risk under certain analytic conditions. HSV does not show a reliable link here. These patterns help refine which viral exposures researchers prioritize when exploring mechanisms or preventive strategies, but they do not change clinical care recommendations by themselves.