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Disease Description

Clinical Questions & Answers on Mumps

Questions and Answers

Q: What causes mumps?

A: Mumps is a viral illness caused by a paramyxovirus of the genus Rubulavirus.

Q: What are the clinical manifestations of mumps?

A: The classic symptoms of mumps include parotitis in about 50% either unilateral bilateral, which develops an average of 16 to 18 days after exposure. Swelling can also be seen in the submandibular and sublingual gland in a small percentage. Nonspecific symptoms including myalgia, anorexia, malaise, headache, and low-grade fever may precede parotitis by several days. As many as 40%–50% of mumps infections are associated with nonspecific or primarily respiratory symptoms, particularly among children less than 5 years of age. Only 30-40% of mumps infections produce typical acute parotitis. In 15-20% of infections, cases are asymptomatic.

Q: Are there other causes of parotitis?

A: Yes, but only mumps causes epidemic parotitis. Parotitis can also be caused by parainfluenza virus types 1 and 3, influenza A virus, Coxsackie A virus, echovirus, lymphocytic choriomeningitis virus, human immunodeficiency virus, and other non-infectious causes such as drugs, tumors, immunologic diseases, and obstruction of the salivary duct.

Q: What is the incubation period and period of infectiousness?

A: The average incubation period for mumps is 16-18 days, with a range of 12–25 days. Fever may persist for 3–4 days and parotitis, when present, usually lasts 7–10 days.

Persons with mumps are usually considered most infectious from 1-2 days before until 5 days after onset of parotitis.

Q: How is the mumps virus transmitted?

A: The mumps virus replicates in the upper respiratory tract and is spread through direct contact with respiratory secretions or saliva or through fomites.

Q: What complications can be caused by mumps?

A: Severe complications of mumps are rare. However, mumps can cause acquired sensorineural hearing loss in children; incidence is estimated at 1 in 20,000 cases. Mumps-associated encephalitis occurs in < 2 per 100,000 cases and approximately 1% of encephalitis cases are fatal.

Some complications of mumps are known to occur more frequently among adults than among children. Adults have a higher risk for mumps meningoencephalitis than children. In addition, orchitis occurs in up to 30-40% of cases in post pubertal males. Although it is frequently bilateral, it rarely causes sterility. Mastitis has been reported in as many as 31% of female patients older than 15 years who have mumps. Other rare complications of mumps are oophoritis and pancreatitis. Aseptic meningitis occurs in 10% of cases and is associated with a good prognosis. Although mumps infection in the first trimester of pregnancy may result in fetal loss, there is no evidence that mumps during pregnancy causes congenital malformations.

Q: What are the long-term effects of mumps?

A: Permanent sequelae such as paralysis, seizures, cranial nerve palsies, aqueductal stenosis, and hydrocephalus are rare, as are deaths due to mumps.

Q: What is the case definition for mumps?

A: The following case definition for mumps was updated and approved by the Council of State and Territorial Epidemiologists (CSTE) in 2011.


  • Parotitis, acute salivary gland swelling, orchitis, or oophoritis unexplained by another more likely diagnosis, OR
  • A positive lab result with no mumps clinical symptoms (with or without epidemiological-linkage to a confirmed or probable case).


  • Acute parotitis or other salivary gland swelling lasting at least 2 days, or orchitis or oophoritis unexplained by another more likely diagnosis, in:
    • a person with a positive test for serum anti-mumps immunoglobulin M (IgM) antibody, OR
    • a person with epidemiologic linkage to another probable or confirmed case or linkage to a group/community defined by public health during an outbreak of mumps.


  • A positive mumps laboratory confirmation for mumps virus with reverse transcription polymerase chain reaction (RT-PCR) or culture in a patient with an acute illness characterized by any of the following:
    • Acute parotitis or other salivary gland swelling, lasting at least 2 days
    • Aseptic meningitis
    • Encephalitis
    • Hearing loss
    • Orchitis
    • Oophoritis
    • Mastitis
    • Pancreatitis
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