I have not taken an MS medications but am JC positive. How can that be?

Here is My Question:
I have not taken any MS meds but recently came up JC positive how is that? 

Answer:
The JC virus (JC stands for John Cunningham) is a ubiquitous virus (meaning it exists throughout the environment,particularly in sewage systems) that most people get exposed to sometime in their life. Exposure is not associated with any specific symptoms, so you will never know if you’ve been exposed without testing.

One such test called the JCV antibody test is done in MS patients to determine their risk of developing PML on prolonged Tysabri treatment. This antibody test is positive in about 60 % of people. Many more people have been exposed to the JC virus, but do not make antibodies against the virus even if the virus  remains latent in their bodies.

There is no known relationship between any disease modifying treatments for MS and JC virus antibody positivity. Therefore, and to answer your question, you do not need to receive any MS treatments to be JCV antibody positive. Furthermore, a positive JCV antibody test does not indicate any disease related to this virus or any problem at all. It only indicates that you are at increased risk of developing a rare brain infection (called PML) if you received prolonged treatment (> 2 years) with Tysabri.

Revere (Rip) Kinkel MD
Professor of Clinical Neurosciences
Director of the Multiple Sclerosis Program
Clinical Neurosciences Director
University of California San Diego