Mononucleosis infection, which is widely known as 'kissing disease', is caused by Epstein-Barr virus. It's most commonly spread through saliva by kissing and sharing drinks, cigarettes, food, drinking cups and utensils. It can also spread through sexual contact and blood transfusions. Its symptoms include fever, inflamed throat, swollen lymph nodes in neck, enlarged spleen, swollen liver and rash.