Also don't forget that antivirals only stop the replication of the virus, they don't kill the virus itself
so even if there would be a benefit, it often comes months later (at least in CFS/ME). By that time, most healthy people catching mono would already have recovered anyway.
so, Rx it a month or two later in a followup appointment if still severely sick... gee, that was easy.
It still might not work. I tried antivirals and they made no difference in my antibody production. (Which is why I favor the theory that it is an immune system dysfunction rather than a chronic viral infection.)