What is mumps?

Mumps is acute, systemic, infectious (communicable) viral disease with the most distinguished feature being swelling of one or both parotid glands (the main salivary glands). Commonly other salivary glands, the meninges, the pancreas, and the gonads are also involved in mumps.

What is the causative agent of mumps?

Mumps is caused by virus (RNA virus), a paramyxovirus, which is pleomorphic and has a diameter of 100 nm to 300 nm (nanometer). The virion (virus particle) of mumps virus is composed of seven proteins and RNA. The RNA is surrounded by envelop made of proteins (generally 4 out of seven proteins) namely an HN (hemagglutinin-neuraminidase), F (hemolysis cell fusion antigen), M (a matrix envelope protein) and an SH protein. Out of seven proteins 3 proteins are present internally and they are, a nucleocapsid protein (NP), a phosphoprotein (P), and a large protein (L). Mumps virus has only one antigenic type, but with some geographical difference in different areas.

Epidemiology of mumps:

Mumps occur generally in winter and spring and epidemic every 2-5 years, especially before vaccine became available in 1967. After the widespread use of mumps vaccine the incidence of mumps has declined by more than 99% fro prevaccination period. Mumps used to be principally a disease of childhood, but these days more than 50% cases of mumps are seen in young adults and occasional outbreak of mumps in confined populations like schools and military barracks.

How mumps is transmitted?

Mumps virus is transmitted by droplet (nuclei, saliva, or fomites) through respiratory route. Mumps can be transmitted before the disease become clinically evident and also by subclinical cases of mumps. Direct contact with mumps patient can also transmit the disease.

How long is the incubation period of mumps?

The incubation period of mumps is generally 14 days to 18 days, but can be from 7-23 days.

What is the status of immunity after an attack of mumps?

An attack of mumps generally confers lifelong immunity and second attack is rare if ever occurs. Long term immunity also develops after vaccination.

What is the pathogenesis of mumps?

Pathogenesis of mumps is not clearly understood as it can rarely cause death and as a result not studied adequately. Replication of the mumps virus in the epithelium of the upper respiratory tract leads to viremia (presence of virus in blood), which is followed by infection of glandular tissues and/or the central nervous system (CNS). The affected glands generally contain perivascular and interstitial mononuclear cell infiltrates with edema. In the salivary glands there is necrosis (death) of acinar and epithelial duct cells.

What are the clinical manifestations of mumps?

In 30-40% of individuals with mumps virus infection there is no clinical manifestation (subclinical infections). General symptoms of mumps are fever, malaise, myalgia, and anorexia (loss of appetite). Parotitis, if it occurs, generally develops within 24 hours of general symptoms. In general parotitis is bilateral, but both the parotid glands may not be affected at the same time and rarely only one parotid gland may be affected. The submaxillary and sublingual salivary glands are less frequently affected in compare to parotid glands and they are always involved bilaterally. In parotitis the patient may complain of earache and it may be difficult to eat, swallow, or talk due to tenderness and obliteration of the space between the ear lobe and the angle of the mandible. The orifice of Stensen's duct (parotid opening in the mouth cavity) is red and swollen in parotitis. The swelling of parotid and other salivary glands increases for a few days and then gradually subsides and generally become normal size within a week.

What are the complications of mumps?

Other symptoms and complications that may develop due to mumps are orchitis (inflammation of testis) in males, which is most common manifestation among postpubertal males affecting approximately 20% of them. The testis in orchitis is painful, tender, and enlarged to several times its normal size and there is fever. Among the affected males (with mumps orchitis) testicular atrophy develops in half of them. Sterility after mumps in males is rare because orchitis is bilateral in less than 15% of affected males. Oophoritis (inflammation/infection of ovary) causes lower abdominal pain in female is less common than orchitis in males, which also do not lead to sterility in affected females.

Aseptic meningitis may develop before, during, after, or in the absence of parotitis and is common in children as well as adults. Symptoms of aseptic meningitis are stiff neck, headache, drowsiness etc. Mumps meningitis is self-limiting ilness, although rarely cranial nerve palsies have led to permanent deafness. More rarely, mumps virus may cause encephalitis, which manifests as high fever with low level of consciousness and frequently results in permanent sequelae. Other CNS problems very rarely associated with mumps include cerebellar ataxia, facial palsy, transverse myelitis, Guillain-Barré syndrome, and aqueductal stenosis.

Pancreatitis may sometimes be a complication of mumps which may present as abdominal pain which may be difficult to diagnose because elevated serum amylase level can be associated with either parotitis or pancreatitis. Other extremely rare complications of mumps include myocarditis, mastitis (inflammation of breast), thyroiditis (inflammation of thyroid gland), nephritis, arthritis, thrombocytopenic purpura etc.

How mumps is diagnosed?

Mumps can be diagnosed easily in patients with acute bilateral parotitis and a history of recent exposure to mumps patient. Laboratory diagnosis is generally required if parotitis is unilateral or absent or when sites other than the parotid gland are involved. Highly sensitive ELISA (enzyme-linked immunosorbent assay) is used for serologic diagnosis of mumps and also for determination of susceptibility to the disease. ELISA can be done with acute- and convalescent-phase sera, which shows significant increase in IgG antibody levels or presence of specific IgM in one serum specimen. Polymerase chain reaction (PCR) can also detect virus from clinical specimens.

Mumps virus can also be isolated from clinical specimens by cell culture. Identification of mumps virus after isolation is rapid by using immunofluorescence in shell vial cultures. Mumps virus can also be isolated (recovered) from saliva, throat, and urine during first few days of illness and from the CSF of patients with mumps meningitis. Mumps patients may also shed the virus in urine for up to 2 weeks.

Differential diagnosis of mumps:

Various diseases can cause symptoms like mumps due to inflammation of parotid glands. Several systemic diseases like influenza A and parainfluenza virus infection, coxsackievirus infection, cat scratch disease, HIV infection, Epstein-Barr virus infection etc. can cause parotitis other than mumps. Drugs, diabetes and Sarcoidosis can also cause patotitis. Parotid inflammation in one side can occur if there is parotid tumor, parotid cyst or obstruction of parotid duct due to stone etc. Bacterial infection also can cause parotitis, like Staphylococcus aureus, Streptococcus species, gram-negative bacteria and certain anaerobes.

Mumps in pregnancy:

Spontaneous abortions are very commonly associated with gestational mumps when the mumps occurs during the first trimester of pregnancy. But mumps in pregnancy does not cause premature birth or fetal malformations.

How mumps is treated?

The treatment of mumps is basically symptomatic. Symptomatic relief can be achieved by use of analgesics (diclofenac, ibuprofen or any other good analgesics) or by application of warm or cold compresses to the parotid area. Mumps immunoglobulin has no role in treatment of mumps. In male patients if there is scrotal pain, gentle support for the scrotum and local application of cold compresses can reduce or minimize scrotal pain. Anesthetic blocks can be used in severe cases. Glucocorticoids are of no use in mumps orchitis (inflammation of testicles). There are some reports that interferon ? alpha may be useful in some cases.

How to prevent mumps?

A live attenuated mumps vaccine (Jeryl Lynn strain) is available at present and a single dose of 0.5 ml intramuscular injection of which induces antibodies that protect the recipient against mumps infection in more than 95% of cases. The immunity is long lasting (probably lifelong). Mumps vaccine is administered as part of measles-mumps-rubella (MMR) vaccine at the age of 12 to 15 months and repeated at age 4-12 years. USFDA has approved use of MMRV (measles-mumps-rubella- varicella) vaccine in 2005 in children of 1-13 years of age and which may replace MMR vaccine soon.

Mumps vaccine (MMR or monovalent mumps vaccine in two doses) is also recommended in susceptible older children, adolescents, and adults, especially male adolescents (increased chance of orchitis) who did not suffer from mumps.

Mumps vaccine is not recommended in pregnant women and also in immunocompromised hosts or patients receiving glucocorticoids. But children with HIV if not severely immunocompromised can safely be immunized against mumps (MMR is used for this).

Inadvertent vaccination of individuals who are already immune (due to natural disease or by active immunization) is not associated with significant adverse reactions. Sometimes fever and parotitis may occur soon after administration of mumps vaccine. Allergic reaction (skin rash and itching) may sometimes occur, which is self limiting.

How to Control mumps?

Control of mumps is difficult as mumps can be transmitted before it becomes clinically evident and a diagnosis can be made and also due to variable incubation period. Control is also very difficult because subclinical infections can transmit and spread mumps. But clinical cases should be isolated till clinical manifestations subside. Articles used by the patient should be disinfected properly and contacts kept under surveillance.