Infection with HSV can cause oral or genital warts, but it can also be fully asymptomatic. There are two types of HSV:

  • herpes type 1 (HSV-1), mainly spread through oral contact
  • herpes type 2 (HSV-2), mainly spread through sexual contact

The World Health Organisation (WHO) estimates that about 64% of people under age 50 worldwide have HSV-1, while an estimated 520 million people in the world have HSV-2.

There’s some evidence that might suggest a possible link between HSV and MS. While there’s a link between HSV infection and the development of MS, experts can’t say with certainty whether HSV can cause MS.

However, HSV may be a possible risk factor for the development of MS.

This association is based on findings of viral genetic material from HSV being present in the tissue samples or body fluids of people with MS.

These findings are more common in people with MS than in individuals without the condition, but researchers don’t have enough evidence currently to explain the mechanism that causes these differences.

A 2023 review of studies looked closely at this possible association previously documented in other studies, and while they were able to establish a connection between these two conditions, more research is necessary to define the role HSV infection can play in the onset of MS.

Other herpes viruses appear to have an association with the development of MS, including:

Another 2023 literature review noted that the pooled prevalence of all the human herpes viruses was 50% in the MS patients participating in these studies. EBV had the highest prevalence, found in 75% of the patients with MS, followed closely behind by VZV at 52% and CMV at 41%.

Researchers concluded EBV, VZV, and CMV are possible risk factors for the development of MS. While HSV had a slightly lower prevalence, at only 32% of the MS patients, the findings are still significant.

Based on the current research, there appears to be an association, but more direct evidence is necessary to further clarify the relationship between infection with HSV and MS.