What system causes sore throat and swollen lymph nodes?

Mononucleosis: Infectious mononucleosis (mono) is often called the kissing disease. The virus that causes mono is transmitted through saliva, so you can get it through kissing, but you can also be exposed through a cough or sneeze, or by sharing a glass or food utensil with someone who has mono. However, mononucleosis isn't as contagious as some infections, such as the common cold.