The objective of the study is to estimate the prevalence of anti-JCV antibodies in multiple sclerosis (MS) participants.

This is a cross-sectional, multi-center, multi-national, epidemiological study to estimate the prevalence of anti-JCV antibody in MS participants. This study will provide an estimate of the prevalence of anti-JCV antibody in the MS population and will investigate inter-country differences.

Key Inclusion Criteria:

• All candidates for this study must have the ability to understand the purpose of the study and provide signed and dated informed consent.
• All patients with a diagnosis of Multiple Sclerosis (MS) of any type, irrespective of their treatment, are eligible to participate once.

Key Exclusion Criteria:

• None

NOTE: Other protocol defined Inclusion/Exclusion criteria may apply.

Multiple Sclerosis (MS) patients will be enrolled in Europe, Canada, and Australia.

Patient enrollment from each country will be commensurate with the distribution of MS patients among all participating countries.