The role of viral infections and other microbial factors in the pathogenesis of multiple sclerosis: a systematic review.
Natalia Morawiec, Bożena Adamczyk, Monika Adamczyk-Sowa
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In 30 seconds
This systematic review assessed studies published from 2020 to 2025 on microbial factors and multiple sclerosis (MS) risk, activity, or progression. It included 61 studies identified through searches of PubMed, SCOPUS, and Web of Science. Epstein-Barr virus (EBV) was the most consistently implicated microorganism: seropositivity was nearly universal among people with MS, and elevated anti-EBNA-1 antibody titers and infectious mononucleosis were associated with MS. Findings for other viruses and bacteria were mixed or limited, while no clear relationship was established for fungal or parasitic infections.
Key findings
- EBV seropositivity was nearly universal among MS patients; studies also reported elevated anti-EBNA-1 antibody titers and an association between infectious mononucleosis and MS development.
- Human herpesvirus-6 may relate to disease activity and interact with EBV-related immune responses, whereas evidence for herpes simplex virus and varicella-zoster virus was inconclusive.
- Some studies suggested cytomegalovirus may be protective; proposed bacterial associations were based on limited evidence, and Helicobacter pylori protection was unconfirmed.
- No clear relationship was established between MS and fungal or parasitic infections.
Why it matters
The review highlights EBV-related immune responses as a prominent infectious correlate in MS research, while showing that evidence for other microorganisms varies substantially. This distinction helps frame microbial factors as part of a complex disease process involving infection, host genetic predisposition, and immune dysregulation, rather than as a single established explanation for MS.
What to keep in mind
The review included studies published only from 2020 to 2025, and the abstract does not report a quantitative synthesis. Evidence for several microbial associations was described as limited or inconclusive.