Hi love, I am also a Tysabri crusader. I’ve been using this form of MS medicine since 2013. Like you, thank God, knock on wood, have been negative. I think I would cry if I couldn’t be on Tysabri anymore. It’s one of the most highly regarded & recommended medications for MS, even though there are a slew of others that have come out. About JCV, you may never become positive. The percentage of people that actually get PML is low and that’s what they monitor you for. If they notice anything in your MRI’s or blood work, they will take you off, immediately and treat you. You won’t be able to go back on Tysabri after. So again, I don’t think you should worry yourself over it. You may never develop it. It’s just really important to talk to your doctor or nurse about your concerns and develop a relationship with them. It will be beneficial for things like this and other situations or questions you might have. Never be afraid to talk to them or ask questions. You’re dealing with a serious illness that you will likely have for a long time. You are not someone to ignore or brush off when you want answers. I believe you shouldn’t worry about it much. Just keep getting your med as long as it’s all good! Hang in there, sweetie! Everything is going to be okay. Just keep your eyes on you. You are the only importance there is. Blessings and good luck to you! ~L~