Mumps

Clinical Description

Identification

An acute viral disease characterized by fever, swelling and tenderness of one or more salivary glands—usually the parotid and sometimes the sublingual or submaxillary glands. Not all cases of parotitis are caused by mumps infection, but other parotitis-causing agents do not produce parotitis on an epidemic scale. Orchitis, most commonly unilateral, occurs in 20%–30% of affected post-pubertal males, but sterility is extremely rare. Mumps orchitis has been reported to be a risk factor for testicular cancer. As many as 40%–50% of mumps infections have been associated with respiratory symptoms, particularly in children aged under five years. Mumps can cause sensorineural hearing loss in both children and adults. Pancreatitis, usually mild, occurs in 4% of cases; a suggested association with diabetes remains unproven.

Symptomatic aseptic meningitis occurs in up to 10% of mumps cases; patients usually recover without complications, though many require hospitalization. Mumps encephalitis is rare (1–2/10 000 cases), but can result in permanent sequelae, such as paralysis, seizures and hydrocephalus; the case-fatality rate for mumps encephalitis is about 1%. Mumps infection during the first trimester of pregnancy has been associated with spontaneous abortion, but there is no firm evidence that mumps during pregnancy causes congenital malformations.

Infectious Agent

Mumps virus, a member of the family Paramyxoviridae, genus Rubulavirus.


Diagnosis

Acute mumps infection can be confirmed through: a positive serological test for mumps-specific IgM antibodies; seroconversion; a significant (at least 4-fold) rise in serum mumps IgG titer as determined by standard serological assay; detection of virus by reverse transcription polymerase chain reaction (RT-PCR); or isolation of mumps virus from an appropriate clinical specimen (throat swab, urine, CSF). In research settings, typing methods can distinguish wild-type mumps virus from vaccine virus. Diagnosis may be more challenging in vaccinated populations where the IgM response may be absent or short-lived and viral load may be lower.


Epidemiology

Mode of Transmission

Airborne transmission or droplet spread; also direct contact with the saliva of an infected person.

Incubation Period

About 16–18 days (range 12–25).

Period of Communicability

Virus has been isolated from saliva (from seven days before the onset of parotitis to nine days afterwards) and from urine (six days before to 15 days after). Maximum infectiousness occurs between two days before onset of illness and four days afterwards. Unapparent infections can be communicable.

Reservoir

Humans.

Susceptibility

Immunity is generally lifelong, and develops after either unapparent or clinical infections.

Occurrence

In unvaccinated populations, about one-third of exposed susceptible people have unapparent or sub-clinical infections, especially young children. In temperate climates, winter and spring are peak seasons. In the absence of immunization mumps is endemic, with an annual incidence usually 100–1 000 per 100 000 population and epidemic peaks every 2–5 years. In many industrialized countries, mumps was a major cause of viral encephalitis. Serosurveys conducted prior to mumps vaccine introduction found that in some countries 90% of persons were immune by age 15 years, while in other countries a large proportion of the adult population remained susceptible. In countries where mumps vaccine has not been introduced, the incidence of mumps remains high, mostly affecting children aged five to nine.

By the end of 2006, 112 of 193 WHO Member States included mumps vaccine in their national immunization schedules. In countries where mumps vaccine coverage has been sustained at high levels, the incidence of the disease has dropped markedly.


Prevention and Control

1)    Preventive measures:

a)    Public education should encourage mumps immunization for susceptible individuals. Routine mumps vaccination is recommended in countries with an efficient childhood vaccination program and sufficient resources to maintain high levels of vaccine coverage. Mumps vaccination is recommended at age 12–18 months, as part of the measles/mumps/rubella (MMR) vaccine, though most countries have a two-dose schedule, with the 2nd dose given at least 1 month after the first dose. More than 90% of recipients develop immunity that is long-lasting and may be lifelong.

b)    Live attenuated mumps virus vaccines are available as monovalent vaccines or trivalent MMR vaccines. Hydrolyzed gelatin and/or sorbitol are used as stabilizers in mumps vaccine, along with neomycin as a preservative. Mumps vaccines are cold-chain dependent and should be protected from light.

c)    Different strains of live attenuated mumps vaccine have been developed in Japan, Russia, Switzerland and the USA. All licensed strains are judged acceptable by WHO for public health programs, except the Rubini strain, which is not recommended because of demonstrated low efficacy; persons who received this strain should be re-vaccinated with another strain. In most industrialized countries, only the Jeryl-Lynn strain or strains derived from it are accepted, because they show no confirmed association with aseptic meningitis.

d)    The reported incidence of adverse events depends on the strain of mumps vaccine. The most common adverse reactions are fever and parotitis. Rare adverse reactions include orchitis, sensorineural deafness, and thrombocytopenia. Aseptic meningitis, resolving spontaneously in less than one week without sequelae, has been reported at frequencies ranging from 0.1 to 100 cases per 100 000 vaccine doses. This reflects differences in vaccine strains and their preparation, as well as variations in study design and case ascertainment. Better data are needed to establish more precise estimates of aseptic meningitis incidence in recipients of different strains of mumps vaccine. The rates of aseptic meningitis due to mumps vaccine are at least 100-fold lower than rates of aseptic meningitis due to infection with wild mumps virus.

e)    Accumulated global experience in industrialized countries shows that 2 doses of vaccine are needed for protection against mumps. The first dose is usually given as MMR vaccine at the age of 12–18 months. The age of administration of the second dose may range from the 2nd year of life to age at school-entry, depending on programmatic considerations aimed at optimizing vaccination coverage. Less commonly, the second vaccination may be delivered through supplementary campaigns in developing countries.

f)    Countries intending to use mumps or MMR vaccine during mass campaigns should give special attention to planning. The mumps vaccine strain should be carefully selected, and health workers should receive training on expected rates of adverse events following immunization, and on community advocacy and health education activities.

g)    Vaccine is contraindicated in the immunosuppressed; however, treatment with a low dose of steroids (less than 2 mg/kg/day) on alternate days, topical steroid use, and aerosolized steroid preparations are not contraindications to administration of mumps vaccine. For theoretical reasons, pregnant women or women planning a pregnancy in the next month (28 days in the USA) should not receive mumps vaccine, although no evidence exists that mumps vaccine causes fetal damage.

2)    Control of patient, contacts and the immediate environment:

a)    Report to local health authority: WHO recommends making mumps a notifiable disease in all countries, Class 3.

b)    Isolation: Respiratory isolation for five days from onset of parotitis. Exclusion from school or workplace until five days after onset of parotitis if susceptible contacts (those not immunized) are present.

c)    Concurrent disinfection: Of articles soiled with nose and throat secretions.

d)    Quarantine: Exclusion of susceptibles from school or the workplace from the 12th until the 25th day after exposure if other susceptibles are present.

e)    Immunization of contacts: Immunization after exposure may not always prevent infection. IG is not effective and not recommended.

f)    Investigation of contacts and source of infection: Immunization of susceptible contacts.

g)    Specific treatment: None.

3)    Epidemic measures:

Immunize susceptibles, especially those at risk of exposure. Serological screening to identify susceptibles is impractical and unnecessary, since there is no risk in immunizing those who are already immune.

4)    Disaster implications:

None.

5)    International measures:

None.

Source: Heymann (Ed.). (2008). Control of Communicable Diseases Manual, 19th edition. Washington, DC: American Public Health Association.


Available Vaccines

WHO-Prequalified mumps vaccines
 

Common Disease Taxonomy: