INTRODUCTION — Mumps is a contagious viral illness that is largely preventable via vaccination . Typically, it begins with a few days of fever, headache, myalgia, fatigue, and anorexia, followed by parotitis; the illness is usually self-limited.
The epidemiology, clinical manifestations, diagnosis, treatment, and prevention of mumps are discussed here. Issues related to vaccination for prevention of mumps are discussed separately. (See "Measles, mumps, and rubella immunization in infants, children, and adolescents" and "Measles, mumps, and rubella immunization in adults".)
EPIDEMIOLOGY — Mumps occurs worldwide; the peak incidence is typically in the late winter to early spring, although sporadic outbreaks occur at any time of year. Mumps occurs most commonly among school-aged children and college-aged young adults; it is rare among infants less than one year of age, who have protection via maternal antibodies.
Before the United States mumps vaccination program began in 1967, about 186,000 cases were reported each year; the actual number of cases was likely much higher due to underreporting. Since implementation of routine vaccination, there has been a more than 99 percent decrease in mumps cases in the United States . (See "Measles, mumps, and rubella immunization in infants, children, and adolescents" and "Measles, mumps, and rubella immunization in adults".)
From year to year in the United States, mumps cases can range from a few hundred to a few thousand (figure 1) [3-6]. The number of cases reported in 2016 and 2017 (6369 and 5629, respectively) were the highest in a decade .
Transmission — Mumps is highly infectious and is transmitted by respiratory droplets, direct contact, or fomites . Mumps spreads rapidly among susceptible individuals living in close quarters, such as young adults living in college dormitories. Infection among school-aged children may be associated with further spread to household family members.
Viral shedding in respiratory secretions precedes the onset of symptomatic illness. The incubation period is usually 16 to 18 days (range 12 to 25 days) from exposure to onset of symptoms . Individuals with mumps are typically infectious from two days before until five days after onset of parotitis [10-12].
Outbreaks — Several sporadic mumps outbreaks (the occurrence of ≥3 cases linked by place and time) have occurred among susceptible individuals in a variety of settings, including military posts , schools [14-16], colleges [17-22], and summer camps [23,24]. There have also been hospital-based [25-27], workplace , and community-based outbreaks .
Factors that contribute to local outbreaks of mumps include closed environments (eg, college dormitories)  and a delay in recognition of mumps by healthcare providers . During outbreaks, mumps cases have occurred among vaccinated individuals ; high vaccination coverage helps limit the size, duration, and spread of mumps. Mumps occurs much more frequently in unvaccinated than vaccinated individuals.
Issues related to management of outbreaks are discussed further below. (See 'Prevention' below.)
CLINICAL MANIFESTATIONS — The incubation period is usually 16 to 18 days (range 12 to 25 days) from exposure to onset of symptoms . Individuals with mumps are typically infectious from three days before until nine days after onset of symptoms [10-12].
Mumps typically begins with a few days of fever, headache, myalgia, fatigue, and anorexia; these manifestations are usually followed by development of salivary gland swelling within 48 hours.
Parotitis occurs most commonly among children between two and nine years of age; tenderness, occasionally associated with earache, typically precedes parotid swelling [33,34]. Parotitis may be unilateral or bilateral; initial unilateral involvement is followed by contralateral involvement a few days later in 90 percent of cases . Parotid swelling can last up to 10 days.
On physical examination, parotid swelling may obscure the angle of the mandible (picture 1), and the orifice of Stensen's duct is erythematous and enlarged (figure 2). Laboratory findings include leukopenia with a relative lymphocytosis and an elevated serum amylase concentration.
Mumps is usually self-limited; most individuals recover completely within a few weeks.
Some patients have nonspecific symptoms and may not present for clinical evaluation [6,33,35]. Asymptomatic infection occurs in 15 to 20 percent of cases; it is more common in adults than in children. Adults who do have symptomatic infection are more likely to have severe manifestations than children with symptomatic infection.
There is no firm evidence for an association between mumps infection during pregnancy and complications [1,36-39].
COMPLICATIONS — Complications of mumps may include orchitis and neurologic manifestations (including meningitis, encephalitis, and deafness); these may occur even among vaccinated individuals who develop mumps . Complications of mumps may occur in the absence of parotitis [15,41,42].
Orchitis or oophoritis — Epididymoorchitis is the most common complication of mumps infection; it occurs among postpubertal males in 15 to 30 percent of cases [1,34,43,44]. Symptoms typically occur 5 to 10 days after onset of parotitis and include abrupt onset of fever (39 to 41ºC) and severe testicular pain accompanied by swelling and erythema of the scrotum. Involvement is unilateral in 60 to 80 percent of cases .
In one mumps outbreak including 11 men (mean age 32 years, range 17 to 55) with mumps orchitis, all required hospitalization for management of testicular pain and swelling . Of these, 82 percent had parotitis approximately 10 days prior to development of orchitis, and 91 percent had never received mumps vaccination. In another series including 67 men with orchitis (unilateral in 90 percent and bilateral in 10 percent), approximately half required hospitalization, and nine patients also had mumps meningitis .
Testicular atrophy has been observed in 30 to 50 percent of unvaccinated patients following mumps orchitis, and decreased fertility has been reported in cases of bilateral orchitis; however, these complications are uncommon and sterility is very rare [46,48]. Sterility has been observed more frequently among men with bilateral orchitis than men with unilateral orchitis . No causal link has been definitively established between mumps orchitis and the subsequent development of testicular cancer; a possible association has been evaluated in several retrospective case series [48,50]. (See "Epidemiology of and risk factors for testicular germ cell tumors".)
Oophoritis develops in 5 percent of postpubertal females with mumps and presents with lower abdominal pain, fever, and vomiting . Mumps has also been associated with mastitis and premature menopause; these are rare . It is unknown whether mumps is associated with female infertility.
Neurologic complications — The most common neurologic complications of mumps include meningitis, encephalitis, and deafness. Prior to widespread vaccination, mumps was a leading cause of viral meningitis and encephalitis as well as the most common cause of acquired sensorineural hearing loss in children [51-56].
Meningitis — Aseptic meningitis is the most common neurologic complication of mumps virus infection; it occurs in 1 to 10 percent of patients [52,68-71] and is three times more common in males than in females [69,72]. Meningitis can occur before, during, or after mumps parotitis. In some series, up to half of patients presented with meningitis in the absence of parotitis [68,72]. Clinical manifestations typically include headache, low-grade fever, and mild nuchal rigidity.
Cerebrospinal fluid (CSF) examination may demonstrate 10 to 2000 white blood cells/microL [53,69,71-73]. The predominating cells are usually lymphocytes, but an early polymorphonuclear predominance may be seen. The CSF total protein concentration is generally normal or mildly elevated. CSF glucose concentration can be mildly depressed, but values below 30 to 40 mg/dL (1.7 to 2.2 mmol/L) have been reported.
Mumps aseptic meningitis generally has a benign course with full neurologic recovery and no permanent deficits. (See "Aseptic meningitis in adults" and "Viral meningitis: Clinical features and diagnosis in children", section on 'Other viruses'.)
Encephalitis — Prior to widespread vaccination, the incidence of mumps encephalitis was approximately 1 in 6000 cases [52,53]. Widespread vaccination has been associated with virtual disappearance of mumps encephalitis.
Patients with mumps encephalitis typically present with fever, altered consciousness, seizures, and partial or complete paralysis [68-71]. As many as one-third of patients present with encephalitis in the absence of parotitis .
Deafness — Most patients with hearing loss associated with mumps present with acute symptoms; occasionally, some exhibit a more gradual clinical course. Unilateral and bilateral involvement has been reported. Symptoms improve in many cases, although permanent deafness has been described [54,56].
Some patients with sensorineural hearing loss during mumps infection develop concurrent vestibular symptoms [78,79]. One patient with acute deafness due to mumps infection noted subsequent development of labyrinthitis and endolymphatic hydrops (Ménière syndrome) .
Other complications — Less common complications occasionally associated with mumps infection include thyroiditis [80-82], myocardial involvement, pancreatitis, interstitial nephritis [83-87], and arthritis [88,89].
●Arthritis – Arthropathy is a relatively infrequent complication of mumps; it affects males more often than females. Both monoarticular involvement (of large joints such as knee and hip) and polyarticular involvement have been described [42,89].
●Pancreatitis – Acute pancreatitis has been described in children and adults with mumps infection [90-92]. The clinical course is typically benign; most cases resolve with conservative management.
●Myocardial involvement – Mumps has been associated with myocardial involvement. Transient electrocardiographic changes including ST segment depression may be observed in up to 15 percent of patients with mumps [53,93,94]. Rare cases of rapidly progressive myocarditis with dilated cardiomyopathy attributed to acute mumps infection have been described [95-100].
Patients with typical manifestations — The diagnosis of mumps should be suspected in patients with typical clinical manifestations (parotitis [or other salivary gland swelling], orchitis, or oophoritis) and relevant epidemiologic exposure (respiratory or household contact with an individual with known or suspected mumps). Individuals who are known to be unimmunized are at highest risk for infection, though mumps should also be suspected among vaccinated individuals with relevant symptoms and signs and epidemiologic exposure. Patients being evaluated for mumps should be placed on droplet precautions. (See 'Prevention' below.)
In the setting of parotitis (or other salivary gland swelling), the diagnosis may be established based on characteristic clinical features. Laboratory testing to establish a diagnosis of mumps is warranted in the setting of extrasalivary gland involvement and/or in the setting of a possible mumps outbreak.
Laboratory confirmation of mumps virus infection may be achieved via one or more of the following [6,101]:
●Positive serum mumps immunoglobulin (Ig)M antibody (typically remains positive for up to four weeks)
●Fourfold rise in serum mumps IgG antibody titer between acute phase and convalescent phase (two to three weeks after symptom onset) serum specimens; this approach is not effective for establishing a diagnosis of mumps infection in previously vaccinated individuals
●Detection of mumps virus by reverse-transcriptase polymerase chain reaction (RT-PCR; performed on serum or buccal or oral swab)
●Detection of mumps virus via culture (performed on buccal or oral swab)
At the initial clinical presentation, two diagnostic specimens should be collected: an acute-phase blood specimen (for serum mumps IgM antibody, acute-phase serum mumps IgG antibody, and serum mumps virus RT-PCR) and a buccal or oral swab (for mumps virus RT-PCR and mumps virus culture). The buccal or oral specimen should be obtained as soon as possible after onset of parotitis (ideally within three days) by gently massaging the parotid gland prior to swabbing the area around Stensen's duct with a synthetic swab.
The IgM response may not be detectable until five days after symptom onset in some cases. Therefore, if the acute-phase serum sample was collected ≤3 days after parotitis onset and is negative for both mumps IgM antibody and mumps virus RT-PCR, serum mumps IgM testing should be repeated on an additional serum sample collected 5 to 10 days after symptom onset.
Collection of a convalescent-phase blood specimen (two to three weeks after symptom onset) for serum mumps IgG antibody testing is warranted for previously unvaccinated individuals with negative serum mumps IgM antibody, negative serum mumps RT-PCR, and negative buccal swab for mumps RT-PCR.
Laboratory confirmation of mumps in individuals with history of mumps vaccination is challenging. In general, serum mumps IgM is negative in approximately half of vaccinated individuals (regardless of the timing of specimen collection). In addition, such patients may have rapid rise of IgG antibody titer; therefore, mumps IgG antibody may be detected at the initial blood draw . In addition, RT-PCR results may be falsely negative since vaccinated individuals may shed lower quantities of virus and may shed virus for a shorter period of time.
Serologic tests cannot differentiate between vaccination and prior mumps exposure, and the level of mumps IgG antibody needed for protection against mumps infection is not known .
Patients with neurologic involvement — The diagnosis of mumps meningitis or encephalitis should be suspected in patients with relevant clinical manifestations (fever, headache, and nuchal rigidity suggest meningitis; fever and altered consciousness suggest encephalitis) and relevant epidemiologic exposure (respiratory droplet or household contact with an individual with known or suspected mumps). Individuals who are known to be unimmunized are at highest risk, though mumps infection should also be suspected among vaccinated individuals with relevant symptoms and epidemiologic exposure.
The confirmation of mumps meningitis or encephalitis can be established via lumbar puncture. Typical cerebrospinal fluid CSF findings are described above. (See 'Meningitis' above.)
Patients with CSF parameters consistent with viral infection warrant further CSF testing with mumps RT-PCR and mumps virus culture. Polymerase chain reaction testing enables prompt diagnosis [103-107]. Mumps virus is most readily isolated from CSF collected during the first three days of symptoms; the techniques are time consuming and may require several days to establish a diagnosis [70,108]. Use of CSF mumps IgM antibody testing has also been described .
Issues related to evaluation of aseptic meningitis and encephalitis are discussed further separately. (See "Aseptic meningitis in adults" and "Viral encephalitis in adults" and "Viral meningitis: Clinical features and diagnosis in children" and "Acute viral encephalitis in children: Clinical manifestations and diagnosis".)
DIFFERENTIAL DIAGNOSIS — The differential diagnosis of mumps includes :
•Other viral causes of parotitis – Viral infections associated with parotitis include influenza A virus, parainfluenza, adenovirus, coxsackievirus, Epstein-Barr virus (EBV), cytomegalovirus, herpes simplex virus, human immunodeficiency virus (HIV), and lymphocytic choriomeningitis virus [111,112]. Viral parotitis may be distinguished from suppurative (bacterial) parotitis by a prodromal period followed by acute swelling of the involved gland, which can last 5 to 10 days and is often bilateral. Viral parotitis does not cause a purulent discharge from Stensen's duct . The approach to diagnosis depends on the clinical presentation (see related topics).
Patients with EBV infection and a positive monospot test may have a cross-reactive false-positive serum mumps IgM antibody test result. This is because the immune response to EBV produces a polyclonal B cell stimulation with broadly reactive cross-reacting antibodies. Among patients with true mumps infection, the likelihood of a cross-reactive false-positive monospot test result is low. (See "Infectious mononucleosis in adults and adolescents".)
•Suppurative (bacterial) parotitis – The microbiology of acute suppurative parotitis is variable and is often polymicrobial; Staphylococcus aureus is the most frequently isolated pathogen. Suppurative parotitis is characterized by sudden onset of firm, erythematous swelling of the pre- and postauricular areas that extends to the angle of the mandible, associated with exquisite tenderness; systemic findings of high fevers, chills, and toxicity are typical. (See "Suppurative parotitis in adults".)
•Noninfectious etiologies of parotitis:
-Salivary gland stone – Sialolithiasis typically presents with pain and swelling; painless swelling may occur. The diagnosis is clinically based on characteristic history and physical examination. (See "Salivary gland stones".)
-Salivary gland tumor – Most patients with salivary gland tumor present with painless mass or swelling. The evaluation includes radiographic imaging and fine needle aspiration. (See "Salivary gland tumors: Epidemiology, diagnosis, evaluation, and staging".)
-Sjögren's syndrome – Sjögren's syndrome may present with a gradual swelling of the parotid or submandibular glands, typically bilaterally. The diagnosis is established based on clinical criteria. (See "Clinical manifestations of Sjögren's syndrome: Exocrine gland disease" and "Diagnosis and classification of Sjögren's syndrome".)
-Sarcoidosis – Extrapulmonary sarcoidosis affecting the parotid glands (up to 5 percent of cases) is characterized by bilateral painless parotid enlargement; the diagnosis is established by clinical and radiographic manifestations and histopathologic detection of noncaseating granulomas. (See "Clinical manifestations and diagnosis of pulmonary sarcoidosis".)
•Other viral causes of orchitis – Viral infections associated with orchitis in children and adolescents include rubella, coxsackie, echovirus, lymphocytic choriomeningitis virus, and parvovirus  (see related topics). (See "Causes of scrotal pain in children and adolescents".)
•Bacterial etiologies – Bacterial causes of epididymitis include sexually transmitted organisms (chlamydia and gonorrhea) and enteric organisms. The diagnosis is established via urine culture and nucleic acid amplification testing for chlamydia and gonorrhea. (See "Evaluation of acute scrotal pain in adults".)
TREATMENT — There is no specific antiviral therapy for treatment of mumps. Management consists of supportive care and may include use of an analgesic/antipyretic agent such as acetaminophen. Parotid discomfort may be managed by application of warm or cold packs. Orchitis may be managed with nonsteroidal anti-inflammatory agents, support of the inflamed testis, and cold packs.
General principles — Control of mumps transmission is challenging since the virus is present in saliva days before clinical parotitis occurs, and viral shedding can occur in asymptomatic individuals.
Hospitalized patients with mumps should be isolated with droplet precautions until the parotid swelling has resolved. Outpatients with mumps should avoid contact with others from the time of diagnosis until at least five days after the onset of symptoms, by staying home from school or work and staying in a separate room if possible . (See "Infection prevention: Precautions for preventing transmission of infection", section on 'Droplet precautions'.)
Mumps infection is largely preventable by immunization prior to exposure. Following mumps exposure, neither postexposure vaccination nor immune globulin has been shown to prevent disease or lessen disease severity (in the absence of an outbreak). (See 'Outbreak settings' below and "Measles, mumps, and rubella immunization in adults".)
Immunization provides incomplete protection from mumps as immunity wanes over time. In one outbreak, the incidence of mumps was lowest among those vaccinated more recently (1.6 cases per 1000 if vaccinated within two years) and highest among those vaccinated more remotely (17.6 cases per 1000 if vaccinated 16 to 23 years earlier) .
Outbreak settings — For individuals who are part of a group identified by public health authorities as being at increased risk for mumps because of an outbreak (the occurrence of ≥3 cases linked by place and time), the approach to immunization is as follows:
●For individuals who are incompletely immunized against mumps, standard vaccination should be administered: two doses of measles, mumps, and rubella (MMR) vaccine separated by at least 28 days. (See "Measles, mumps, and rubella immunization in adults".)
It is reasonable to exclude incompletely immunized students from schools affected by a mumps outbreak with readmission following vaccination. Given the incubation period of 12 to 25 days between exposure and onset of symptoms, incompletely immunized individuals should stay home from the 12th day after mumps exposure through the 26th day after the onset of parotitis in the last person with mumps in the affected setting .
●For individuals who completed a two-dose series of a mumps virus-containing vaccine prior to outbreak onset, we suggest a third MMR.
In January 2018, the Advisory Committee on Immunization Practices (ACIP) recommended that individuals who are identified by public health authorities as being part of a group at increased risk for mumps because of an outbreak who were previously vaccinated with two doses of MMR vaccine receive a third MMR dose .
The benefit of third MMR dose increases with time since receipt of the second MMR dose ; therefore, it is reasonable to prioritize booster vaccination to those who have had longer intervals since their previous MMR immunization.
The approach to administration of a third MMR dose is supported by several observational studies [114,116-118]. In one study including 20,496 enrolled university students, 259 students were diagnosed with mumps during an outbreak (12.6 cases per 1000); 98 percent of students had received at least two doses of MMR vaccine prior to the outbreak [114,118]. A vaccination campaign was initiated targeting 19,705 students who had received no more than two doses before the start of the outbreak; 4783 students received a third MMR dose in the context of the outbreak. The attack rate was lower among the students who received three MMR doses than those who received two MMR doses (6.7 versus 14.5 cases per 1000 population; p <0.001). A multivariable regression analysis was performed with adjustment for the amount of time following the third MMR dose and the time since receipt of the second MMR dose; at seven days after receipt of a third MMR dose, booster vaccination was associated with a 60 percent lower risk of mumps than receipt of a second MMR dose (adjusted hazard ratio 0.40; 95% CI 0.26-0.62). The mumps attack rate was lowest among students who had received their second dose of MMR within two years of the outbreak, compared with those who completed the two-dose MMR series more than two years earlier.
The available evidence is not sufficient to fully characterize the effect of a third MMR dose on reducing the size or duration of an outbreak, and the duration of additional protection conferred by a third MMR dose is not known .
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Immunizations in adults".)
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SUMMARY AND RECOMMENDATIONS
●Mumps occurs worldwide. Since implementation of routine vaccination in the United States, there has been a more than 99 percent decrease in mumps cases; a few hundred to a few thousand cases continue to occur each year (figure 1). During outbreaks, mumps cases have occurred among vaccinated individuals; however, high vaccination coverage helps limit the size, duration, and spread of mumps. (See 'Epidemiology' above and 'Outbreaks' above.)
●Mumps virus is highly infectious and is transmitted by respiratory droplets, direct contact, or fomites. Viral shedding in respiratory secretions precedes the onset of symptomatic illness. The incubation period is usually 16 to 18 days (range 12 to 25 days) from exposure to onset of symptoms. Individuals with mumps are typically infectious from three days before until nine days after onset of symptoms. (See 'Transmission' above.)
●Mumps typically begins with a few days of fever, headache, myalgia, fatigue, and anorexia; these symptoms and signs are usually followed by development of salivary gland swelling within 48 hours. Parotitis may be unilateral or bilateral; initial unilateral involvement may be followed by contralateral involvement a few days later. Parotid swelling can last up to 10 days. Mumps is usually self-limited; most individuals recover completely within a few weeks. (See 'Clinical manifestations' above.)
●Complications of mumps include orchitis or oophoritis, neurologic manifestations (including meningitis, encephalitis and deafness), and other less common complications. Complications of mumps may occur in the absence of parotitis. (See 'Complications' above.)
●The diagnosis of mumps should be suspected in patients with typical clinical manifestations (parotitis [or other salivary gland swelling], orchitis, or oophoritis) and relevant epidemiologic exposure (respiratory or household contact with an individual with known or suspected mumps). Individuals who are known to be unimmunized are at highest risk for infection, though mumps should also be suspected among vaccinated individuals with relevant symptoms and epidemiologic exposure. Patients being evaluated for mumps should be placed on droplet precautions. (See 'Diagnosis' above.)
●In the setting of parotitis (or other salivary gland swelling), the diagnosis may be established based on characteristic clinical features. Laboratory testing to confirm a diagnosis of mumps is warranted in the setting of extrasalivary gland involvement and/or in the setting of a possible mumps outbreak. Laboratory diagnosis of mumps virus infection may be achieved via serology, reverse-transcriptase polymerase chain reaction (RT-PCR), or culture. At the initial clinical presentation, two diagnostic specimens should be collected: an acute-phase blood specimen and a buccal or oral swab. (See 'Diagnosis' above.)
●There is no specific antiviral therapy for treatment of mumps. Management consists of supportive care and may include use of an analgesic/antipyretic agent such as acetaminophen. Parotid discomfort may be managed by application of warm or cold packs. Orchitis may be managed with nonsteroidal anti-inflammatory agents, support of the inflamed testis, and cold packs. (See 'Treatment' above.)
●For individuals who are part of a group identified by public health authorities as being at increased risk for mumps because of an outbreak and who previously completed a two-dose series of mumps virus-containing vaccine prior to outbreak onset, we suggest a third MMR dose (Grade 2C). Incompletely immunized individuals should receive the standard two-dose MMR series. (See 'Outbreak settings' above and "Measles, mumps, and rubella immunization in adults".)
●Mumps infection is largely preventable via immunization prior to exposure. Following mumps exposure, neither postexposure vaccination nor immune globulin has been shown to prevent disease or lessen disease severity. (See 'Prevention' above.)