How did Quinn and Finn get mono from Santana, but Santana was not sick?

In season2 episode12, Silly Love Songs in Glee,


Santana gives Finn mono whom gives it to Quinn when they kiss on the same day


so how come Santana is not sick as well the next day, seeing as it was important to the storyline?|||In the episode she says that she has had mono so many times she has built up an amunity to it. In real life, while this is possible, it would also be possible that she would be a carrier. Somebody who carries the disease but exhibits no symptoms.|||she's immune to the disease since she's had it several times before ("i've had mono so many times, it turned into stereo").|||She holds her breath as you can find out on the glee official fansite i hope this helped