How could my girlfriend have caught mono?

Contagious: It is not just a "kissing" disease. She may have been in close physical proximity to someone with mono or used a contaminated utensil, glass etc.

Transfer: Mono like many viral illnesses is often contageous before the person knows they are sick. It will end up in their saliva which may pass to their fingers when they touch their face.It then will contaminate any surface/object/doorknob/banister etc that it touches. People often pick up these germs by touching objects & then touching their face/mouth.This can be transmitted intimately but often is not