Mumps

Etiology and Pathogenesis Top

1. Etiologic agent: Mumps virus, an enveloped RNA virus in the Paramyxoviridae family. It enters the respiratory system (initially replicating in the respiratory epithelium), causes viremia, and infects multiple organs and tissues (including the salivary glands and central nervous system).

2. Reservoir and transmission: Humans are the only reservoir for mumps virus. The virus is transmitted from a person with mumps or asymptomatic infection via droplets as well as by direct or indirect contact with contagious biological material (blood, saliva, cerebrospinal fluid, urine) or contaminated objects.

3. Incubation and contagious period: The incubation period is from 12 to 25 days (typically 16-18 days). Patients may have viral shedding in the saliva up to 7 days before the onset of parotitis and up to 9 days afterwards (virus shedding in urine is observed for up to 2 weeks).

Clinical Features Top

In up to a third of patients, mumps is either asymptomatic or subclinical with only mild respiratory tract symptoms. Symptomatic mumps virus infections have a sudden onset and acute course. All of the following signs and symptoms may occur simultaneously, separately, or in various combinations.

1. Prodromal phase (influenza-like symptoms): Rarely observed in children, but more frequent in adults; it occurs 1 to 7 days prior to parotitis.

2. Parotitis is the most common presentation (60%-70%); the submandibular salivary glands are affected less frequently (10%). Although it may often present with unilateral swelling, ultimately most cases progress to bilateral involvement (~70%). The clinical manifestations of parotitis include the following:

1) Pain and swelling of the salivary glands, which is most pronounced on day 2 or 3; typically the gland is soft (pitting edema), though occasionally it may be firm. The skin above the gland is taut, but of otherwise normal appearance. The swelling gradually extends to the surrounding tissues (temporal area, zygomatic arch, mastoid process, neck) causing an outward displacement of the earlobe. The symptoms begin to subside within 3 to 4 days and resolve within ~7 days.

2) Characteristic appearance of the buccal mucosa: Erythema and edema around the orifice of the parotid duct.

3) Earache on the side of involvement.

4) Decreased production of saliva (“dry mouth” sensation), parotid pain exacerbated by consumption of acidic foods (or any other products that stimulate the production of saliva).

5) Difficulties in chewing, swallowing (dysphagia), and opening the mouth.

6) Fever (38-39 degrees Celsius) appears simultaneously with glandular swelling and persists for 3 to 4 days; it recurs when a new salivary gland becomes involved or complications develop. Young children may remain afebrile.

7) Other signs and symptoms: Malaise and fatigue, headache, appetite loss, vomiting.

3. Mumps meningitis: Cerebrospinal fluid pleocytosis is observed in over half of patients with mumps parotitis, most of whom do not have symptoms of meningitis or encephalitis. The majority of cases are either associated with minor symptoms or asymptomatic. Clinical features of meningitis occur in 5% to 10% of patients, more frequently in adults and males, usually between day 4 and day 8 of infection (less commonly before the onset of parotitis or during convalescence). Signs and symptoms are usually mild and resolve within 1 week; however, more severe sequelae can occur (eg, deafness, paresis, hydrocephalus) and mortalities have been reported at a rate of ~1%. Up to half of meningitis cases occur in the absence of parotitis.

Diagnosis Top

Typical cases can be diagnosed on the basis of supportive medical history, exposure history, and physical examination, but given the current rarity of the infection and that other infectious agents can cause similar presentations, laboratory confirmation is generally sought. Given that even the administration of 2 doses of the vaccine is not 100% effective, in regions of high vaccination coverage many cases occur in fully vaccinated individuals and therefore vaccination history cannot be used to exclude the diagnosis.

Diagnostic Tests

1. Biochemistry: Increased serum and urinary amylase levels support the involvement of salivary glands.

2. Complete blood count: The white blood count is often low with a relative lymphocytosis.

3. Serum serology: This is only reliable in nonvaccinated individuals. Positive IgM response in the acute phase of the disease and/or a ≥4-fold increase in specific IgG levels between acute and convalescent sera are generally diagnostic. In vaccinated patients who develop mumps, IgG levels may be elevated in the acute period and IgM may not appear, and therefore serologic diagnosis is often not possible.

4. Detection of mumps virus: Mumps virus is detected either through culture or detection of viral RNA using reverse transcriptase–polymerase chain reaction (RT-PCR). Suitable specimens include buccal (around the duct of Stensen) or pharyngeal swabs, blood, urine, and cerebrospinal fluid. The sooner the sample is collected after the symptom onset, the higher the yield.

Differential Diagnosis

1. Other infectious causes of parotitis: Viral (parainfluenza virus, influenza virus, cytomegalovirus, enteroviruses, lymphocytic choriomeningitis virus, HIV, Epstein-Barr virus); bacterial, including abscess (most frequently Staphylococcus aureus, anaerobes, and gram-negative bacteria, less frequently Mycobacterium and Actinomyces; purulent drainage may be present around the orifice of the parotid duct, appearing spontaneously or after applying pressure to the involved gland); cat-scratch disease (anterior auricular lymphadenopathy, Parinaud syndrome); toxoplasmosis.

2. Noninfectious causes of parotid gland enlargement: Sialolithiasis, ductal obstruction (in patients with recurrent obstruction, perform ultrasonography, sialography, or both); cyst, angioma, or salivary gland tumor (perform ultrasonography, histologic examination, or both); Sjögren syndrome, Waldenström macroglobulinemia, sarcoidosis; drug-induced allergic reactions (iodides, guanethidine, phenylbutazone, thiouracil); trauma; cystic fibrosis; amyloidosis.

3. Diseases affecting the adjacent tissues and organs: Lymphadenopathy, bone tumors (eg, mandibular tumor), arthritis of the temporomandibular joint, hypertrophy of the sternocleidomastoid muscle.

4. In patients with meningitis and no signs of parotitis: Other types of aseptic meningitis (of a viral or tuberculous etiology).

Treatment Top

Antiviral Treatment

No specific antiviral treatment is available.

Symptomatic Treatment

Antipyretics and analgesics when necessary (acetaminophen [INN paracetamol], nonsteroidal anti-inflammatory drugs). Adequate hydration, mouth rinsing, avoidance of sour-tasting foods.

Complications and Less Common PresentationsTop

Adults are at higher risk of complications of mumps than children. Complications may develop during the acute disease phase, convalescence, or even later; rarely, they may precede parotitis or are the only manifestation of the disease. Note: Recurrence of fever and vomiting in the course of mumps suggests the development of complications.

1. Epididymo-orchitis: Unilateral or bilateral, it affects 30% to 40% of pubertal boys and young men with mumps and usually occurs at the end of the first week of the disease (frequently accompanied by meningitis). Epididymo-orchitis may affect spermatogenesis and cause infertility (this is a rare complication, usually resulting from bilateral infection).

Signs and symptoms: Sudden onset, fever, severe testicular pain with referred perineal pain, testicular edema, erythema and warming; lower abdominal pain, headache, chills, nausea, and vomiting. The symptoms usually persist for 4 days. Orchitis can occur prior to or in the absence of parotitis. Mumps virus RNA can be detected in seminal fluid weeks after infection. Differential diagnosis: bacterial epididymo-orchitis (chlamydia, syphilis, gonorrhea, tuberculosis), testicular torsion, injury.

Treatment: Symptomatic treatment includes analgesics (in some cases even opioids may be necessary), suspensory garment (or tight underwear), bed rest, which may alleviate the pain, and ice packs. Glucocorticoids are not effective and may worsen the course of parotitis and increase the risk of secondary bacterial infection.

2. Oophoritis: Unilateral or bilateral, it affects 5% to 7% of postpubertal girls and women. Signs and symptoms are less severe than in the case of epididymo-orchitis and are more like those of acute appendicitis (lower abdominal pain or tenderness). Oophoritis is not believed to cause infertility.

3. Pancreatitis: Affects <10% of patients, usually occurs in the later phases of the disease (up to a few weeks after parotitis). Approximately one-third of patients with pancreatitis have no concomitant parotitis.

Signs and symptoms: Acute upper abdominal pain (may be accompanied by referred left abdominal and back pain), nausea and vomiting, fever and chills, diarrhea; increased serum lipase levels (in parotitis, blood and urine amylase levels are also increased). Usually, pancreatitis resolves spontaneously within 7 days.

Symptomatic treatment: see Acute Pancreatitis. Opioid analgesics may be necessary in some cases.

4. Other (rare) complications:

1) Neurologic: Guillain-Barré syndrome, transverse myelitis, polyneuropathies, labyrinthitis, facial nerve palsy, hearing loss.

2) Ophthalmologic: Conjunctivitis, dacryoadenitis, scleritis, keratitis, uveitis/iritis, optic neuritis.

3) Hematologic: Thrombocytopenia, paroxysmal nocturnal hemoglobinuria.

4) Other: Thyroiditis, arthritis (0.4% risk, usually affects large joints), myocarditis, thymitis, hepatitis with acute cholecystitis, mastitis, nephritis; infection during the first trimester of pregnancy increases the risk of miscarriage.

Prognosis Top

In the majority of cases, the prognosis is favorable and depends on the type of complications (see Complications and Less Common Presentations, above). Mumps usually confers lifelong immunity; a second mumps infection is extremely rare. Recurrent parotitis most frequently develops in patients with ductal obstruction (perform sialography) or immunodeficiency (cytomegalovirus or human immunodeficiency virus infection, Sjögren syndrome). Infection during pregnancy does not increase the risk of malformations.

Prevention Top

1. Vaccination is the key prevention method (see Vaccines: Measles, Mumps, and Rubella). Two doses of mumps-containing vaccine administered after 1 year of age are recommended given the reduced effectiveness of 1 dose (estimated at ~80%). There is also evidence of some waning immunity with age.

2. Exposed individuals: Mumps vaccine given after exposure has not been shown to reduce the risk of developing disease.

3. Suggest limitation of social contacts to decrease the propagation of infection for 5 days following the onset of parotitis.

4. Hospitalized patients: Droplet precautions are recommended until 9 days after parotid swelling.