The Epstein-Barr virus (EBV) is a type of herpesvirus, which is very common worldwide. It's best known for causing infectious mononucleosis, often referred to as "mono" or the "kissing disease." However, EBV can also be associated with various other illnesses, including some forms of cancer.

EBV is most commonly spread through bodily fluids, primarily saliva. This is why mononucleosis, which is a common manifestation of an EBV infection, is often associated with young adults and teenagers, as it can be spread through kissing. However, EBV can also be spread through other means such as sharing drinks or utensils.

Most people are infected with EBV at some point in their lives, often during childhood. In many cases, the infection goes unnoticed or causes mild symptoms that aren't recognized as being caused by EBV. Once a person has been infected with EBV, the virus remains in the body for life, usually in a dormant state. It can, however, reactivate, usually without causing symptoms.

Symptoms of an active EBV infection, like infectious mononucleosis, can include fever, sore throat, swollen lymph nodes, fatigue, and swollen spleen or liver. These symptoms can vary in severity and duration.

EBV has also been linked to certain types of cancers, such as Burkitt's lymphoma, Hodgkin's lymphoma, and nasopharyngeal carcinoma, as well as to conditions like multiple sclerosis. However, it's important to note that most people who have EBV will not develop these serious conditions.

There's no specific treatment for EBV itself. Treatment generally focuses on relieving symptoms. In cases where EBV is associated with cancer or other serious conditions, treatment would be targeted towards those specific conditions.