Human herpesviruses in MS.

Environmental factors operate on a background of genetic susceptibility in MS pathogenesis; the human herpesviruses (HHV) are likely candidates for such factors. HHV share a number of properties: they are almost ubiquitous, they are highly prevalent worldwide, they all cause latent infections and they are capable of reactivation. Epstein Barr virus (EBV), HHV-6A and varicella zoster virus (VZV) are consistently linked with MS, particularly with respect to epidemiology, antibody responses in serum (EBV) and cerebrospinal fluid (EBV and HHV-6A), and with MS exacerbations that are associated with viral reactivation (VZV, HHV-6A and EBV). HHV have the potential for a causal role in MS--they may be key players in the disease process--and this role could be mediated through several direct or indirect mechanisms.