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Having previously tested positive for the JC virus is definitely something worth keeping on your radar. Testing positive means the virus is present in your body in a latent (dormant) state — and it can stay that way indefinitely.

The key factor that raises PML risk isn't just having the JC virus, but rather having a Show Full Answer

Having previously tested positive for the JC virus is definitely something worth keeping on your radar. Testing positive means the virus is present in your body in a latent (dormant) state — and it can stay that way indefinitely.

The key factor that raises PML risk isn't just having the JC virus, but rather having a suppressed immune system that allows it to reactivate. So the bigger question is: what MS treatment are you on now? Here's what's important to know:

- If you're currently on an immune-suppressing DMT, your neurologist should be monitoring your JC virus antibody levels every 6 months
- Higher antibody levels (called the JC index) indicate a greater risk of PML
- Some MS medications carry a higher PML risk than others — Tysabri being among the highest, which is likely why you were taken off it

The good news is that being off Tysabri removes one of the biggest risk factors. Your neurologist can assess your current risk based on your antibody levels and whatever treatment you're on now.

It's really worth having a direct conversation with your neurologist about your JC status and how it should factor into your current treatment plan.

 AI-generated responses are not a substitute for medical advice. These services are not intended to diagnose, treat, or cure any condition or disease. Always ask your doctor about specific health concerns.

JC Virus, PML, and Multiple Sclerosis