Because of widespread vaccination efforts, its role as a major cause of childhood morbidity has greatly diminished. Humans are the only natural host. Infection is uncommon under the age of 1 year, and congenital infection is rare but can lead to fetal loss in the first trimester. Virus is shed in saliva from as long as 6 days before to 5 days after clinical onset.
Initial replication occurs in the pharynx, followed by viremic dissemination.
Both humoral and cell-mediated immune responses are induced and correlate with cessation of viremia and salivary virus excretion. Two thirds of cases are symptomatic, with initial symptoms of malaise and fever predominating. Painful swelling of the parotid gland is the characteristic feature of infection. It may be unilateral, and other salivary glands may be involved. Subsequent sterility is uncommon, although testicular atrophy may occur.