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Disease Description

Clinical Questions & Answers on Mumps

What causes mumps?
What are the clinical manifestations of mumps?
Are there other causes of parotitis?
What is the incubation period and period of infectiousness?
How is the mumps virus transmitted?
What complications can be caused by mumps?
What are the long-term effects of mumps?
What is the case definition for mumps?

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 salvia 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 approved by the Council of State and Territorial Epidemiologists (CSTE) in 2008.

Laboratory criteria for diagnosis

Isolation of mumps virus from clinical specimen, or
Detection of mumps nucleic acid (e.g., standard or real time RT-PCR assays), or
Detection of mumps IgM antibody, or
Demonstration of specific mumps antibody response in absence of recent vaccination, either a four-fold increase in IgG titer as measured by quantitative assays, or a seroconversion from negative to positive using a standard serologic assay of paired acute and convalescent serum specimens.

Case Classification Suspected

A case with clinically compatible illness or that meets the clinical case definition without laboratory testing or a case with laboratory tests suggestive of mumps without clinical information.

Probable

A case that meets the clinical case definition without laboratory confirmation and is epidemiologically linked to a clinically compatible case.

Confirmed

A case that: 1) meets the clinical case definition or has clinically compatible illness, and 2) is either laboratory confirmed or is epidemiologically linked to a confirmed case.