The most common symptoms are fever, headache, muscle aches, and loss of appetite followed by swelling of the salivary glands under the ears-- on one or both sides (known as parotitis). Symptoms usually appear between 12 and 25 days after exposure to the virus. However, about one-third of infected people do not have symptoms. Parotitis occurs only in 30%-40% of individuals infected with mumps.
Mumps is diagnosed by a combination of symptoms and physical signs and laboratory confirmation of the virus, as not all cases develop characteristic parotitis and not all cases of parotitis are caused by mumps.
In children, mumps is usually a mild disease. Adult service members may have a more serious form of the disease and more complications.
Serious complications of mumps are more common among adults than among children. Mumps can lead to hearing loss, aseptic meningitis (infection of the covering of the brain and spinal cord) in about 10% of cases, painful, swollen testicles in 20-30% of males who have reached puberty (orchitis) but rarely does this lead to fertility problems, and painful, swollen breasts in about 30% of women who have reached puberty (mastitis), and in a very few cases, inflammation of the ovaries. An increase in spontaneous abortion (miscarriage) has been found among women who developed mumps during the first trimester of pregnancy; however, there is no evidence that mumps causes birth defects. Deafness, in one or both ears, can occur in approximately one per 20,000 reported cases of mumps.