Smooch! You may have heard mononucleosis, or mono, called the kissing disease. That's because someone who has this infection can pass it to others by kissing them. But it also can spread when people with mono share toothbrushes, straws, or anything that might have their saliva on it.
Mono can make someone feel super tired and also has a lot of the same symptoms as the flu — a fever, sore throat, and headaches. Kids who have mono need to rest a lot to get better.