There have been many many studies looking for a viral cause for rheumatoid arthritis. But, none of them have proven that viruses are the cause. Maybe that’s because we are looking too late. We know now that the immune system is activated in RA long before the joint symptoms of pain and swelling. So, if a virus causes RA, the only way we might be able to prove it is to know in advance who is going to get RA down the road, and study those folks. The problem is we don’t know exactly who is going to get it !!