Nah, you misunderstood me.

It's not caused by herpes, it is caused (sometimes) by the "kissing disease", aka severe teenage herpes 4, aka mononucleosis. An EBV test won't really tell you anything now, since just about everyone has had herpes 4 in one form or another, and has hhv4 antibodies bouncing around their system - 90%+ in their childhood, when it occurs like a mild three-day flu, and the rest in adolescence, from their first kiss with anyone of the other 90%. In adolescence, though, this stuff takes a month to clear up and is a major disease, not a little 3-day flu.

Basically, teenage mono is strong enough to bugger up your lymphatic system for its duration and then some, which lets fungi move in and start making themselves at home. Couple years later, you get your first yeast infection and start not tolerating familiar foods...