Multiple sclerosis onset preceding Epstein-Barr virus infection

Epstein-Barr virus (EBV) infection is proposed to be a requisite exposure for multiple sclerosis (MS) development.1 However, the strongest epidemiologic evidence for this was derived from a US military cohort that was predominantly male and White, thus unrepresentative of the wider MS population.2 Cases have been reported of people with MS who tested negative for EBV nuclear antigen 1 (EBNA-1) and EBV viral capsid antigen (VCA) immunoglobulin G (IgG) antibodies, including 82 of 1039 individuals (7.9%) in a multicenter cohort study (2001-2023).3,4 We aimed to identify and characterize any cases of primary EBV infection after MS onset in a large population-based cohort, which has not been done previously.