I have had Epstein-Barr virus (about 12 years ago) and at the time was misdiagnosed (was told it was "post flu" syndrome). I was so exhausted I couldn't even get out of bed, and was off work for over a month. It wasn't until about 6 years later when I had pre surgical blood work done that my doctor told me I carried the virus in my system. Since it's in the same family of viruses as mononeucleosis, I guess I will always be at risk for another bout, although I never have since. I was never given any kind of medication, but at the time, Epstein-Barr was a fairly new thing. Funny thing is, I read all the literature that I could get my hands on but my doctors kept pooh-poohing my theory. (And I worked with these doctors too....)I do know that your system can be so exhausted from Epstein Barr that it's unable to fight off anything else, and I ended up with a roaring case of strep throat immediately after I started improving. If your dad is older, he may just be having all kinds of things attacking his system with not a lot of strength to fend anything off. It really is a horrible virus, I couldn't believe how weak and exhausted I was 24/7.