I Took My Son To The Doctor Because He Has

I took my son to the doctor because he has been running a low grade fever (less than 101) on and off for a couple of weeks. He is also tired, and has headaches. They did a urine test, and said he had blood in the urine, but no white cells. He was negative for strep. The doctor left a message on the machine that said he showed signs of Epstein barr in the past, but was not actively infected. What does that mean? Can that cause blood in the urine, or is that a separate issue?