I found a very interesting site about EBV and autoimmune diseases in general. The section that talks about autoimmune thyroid is 5.5, and is on page 4 of the report. *Warning thingy* This is a PDF file, and may load slow on dial-up. Make sure you have Adobe or something similar, or you can't read it.
Some researchers have a theory that teens who have nasty bouts of mononucleosis (caused by EB virus) are more likely to come down with Hashi's later in life. They believe the EB virus sets up an autoimmune response that causes other problems. It's only theory, though, and there are lots of other theories that make just as much sense. It'll be a long time before it's proven, IMO.
I was 12 when I had a nasty bout with mono. I was sick for months, then when I started to feel better, I got sick again. Everything anybody had would make its way to me. Mono, strep throat, bronchitis, etc., I had them all in the course of 4 months...24 years later, it's "Welcome to Hashimoto's" for me.
I have antibodies for EBV which means I had it at one time. But, I had no idea I had it when I did so not sure when it was. I only know because I had bloodwork done this summer including that. The EBV was not active at that time. Anyway, I have thyroid issues and am not sure how it's related.
Midwest is correct, if your immune system stays healthy it will never become active but when it becomes weakened is when the virus comes out of dormency and becomes active.
I went untreated hypo for three years due to stupid docs and was working a very physical job and it finally took its toll and when I finally crashed I ended up with a massive case of EBV that landed me in bed for nearly six months. I think the hypo and resulting adrenal fatigue as well as candida literally wiped out my immune system allowing the EBV to become active.