Mumps is a common viral disease causing swelling of the parotid salivary glands, and occasionally inflammation of the pancreas, an ovary, or a testis. Mild fever, headache, and malaise may precede the gland swelling. It is an incubation period of 21 days. Rarely a viral meningitis and less often encephalitis complicate mumps. The symptoms are more serious in adults and very rarely a bilateral and severe testicular inflammation can cause sterility. Children over 18 months of age can be vaccinated against, measles, and rubella (MMR vaccine). One attack of mumps generally confers lifelong immunity.