Specifically, EBV infects oropharyngeal epithelial cells, causing pharyngitis and releasing infectious viruses that invade B lymphocytes in the area. Mature EBV is rarely replicated by B lymphocytes. Indeed, if mature virus is made, the lymphocyte dies. This secondary response, which normally persists for life, controls the EBV-induced proliferation of infected B cells. The earlier in life EBV infection occurs, the milder the illness.
Viral transmission is thought to be mainly salivary exchange in one way or another.
In adolescents, this is thought to be by intimate kissing, although, in theory, sharing toothbrushes or cups could transmit virus. Quarantine is unwarranted. The incubation period is 30 to 50 days, making it difficult to pinpoint contacts. Petechiae on the posterior palate are suggestive but not pathognomonic. Swollen eyelids are common.