--is positive in almost everyone beyond the age of 30; all it indicates is that one has been infected with this omnipresent virus at some point in the past.

There are patterns of antibody occurrence with EBV that might indicate a reactivation or a more recent infection; these are more likely to be correlated with symptoms:

http://www.cdc.gov/ncidod/diseases/ebv.htm

http://jcm.asm.org/cgi/content/full/47/10/3204