Today, my boyfriend of about a month and a half went to the hospital and was diagnosed with mono. He's been sick for well over a week already and I'm fairly certain we've had enough close contact that I've contracted the virus as well (no symptoms as of yet).

My question is: Can I start taking some sort of medecine to combat the virus now or do I have to wait for symptoms to appear?

I have had mono before, about 5 years ago and subsequently had my tonsils taken out. I don't expect the symptoms this time around would be as bad since I don't have my tonsils, but I would rather avoid them altogether if at all possible.