Mumps is mainly a mild childhood infection of 5 to 9-year-olds, but can affect adults as well. Infection in adults is associated with more severe complications than kids.
Mumps are caused by the mumps virus – a single-stranded RNA virus belonging to the Paramyxovirus family.
Mumps are spread through respiratory droplets released when an infected person sneezes or coughs, or through direct contact with saliva, respiratory droplets or objects handled by an infected person. The mumps virus enters the body through the nasal passages or mouth and replicates in the nasopharynx and lymph nodes. Twelve (12) to 25 days later, the virus enters the bloodstream (viremia) and spreads to a number of tissues and glands (meninges, salivary, pancreas, testes and ovaries). Inflammation of the infected tissues results in the characteristic symptoms of mumps. Inflammation of the parotid salivary glands (parotitis) near the jaw line of the cheek occurs in up to 40% of those infected. Parotitis may be unilateral (one-side) or bilateral (both sides) resulting in the characteristic puffy-jaw chipmunk appearance associated with mumps infection.
Initial symptoms of mumps infection occur 12 to 25 days following exposure and are nonspecific:
- fever,
- headache,
- muscle aches,
- fatigue,
- and loss of appetite.
Swelling of salivary glands usually follows 2-3 days after the appearance of initial symptoms, and symptoms generally resolve within 10 days. Not everyone who is infected with the mumps virus develops symptoms: up to 20% of cases are asymptomatic. In addition, up to half of those infected may present with nonspecific symptoms or symptoms of a respiratory infection.
Infected individuals are infectious up to 3 days before the appearance of symptoms, and for approximately 9 days following the appearance of symptoms.
Complications of mumps infections are rare and with the exception of deafness are more common in adults than in children.
Complications of mumps infection can include:
- inflammation of the brain [encephalitis] (<2/100,000),
- inflammation of the tissue covering the brain and spinal cord [meningitis] (up to 10%),
- inflammation of the testicles (orchitis)(up to 50% of post-pubertal males),
- inflammation of the ovaries [oophoritis] and/or breasts [mastitis] (5% of post-pubertal females)
- spontaneous abortion,
- deafness, usually permanent [1/20,000],
- pancreatitis (rare).
Vaccination is the cornerstone of mumps prevention: children should receive 2 doses of measles-mumps-rubella vaccine (MMR), the first at 12-15 months of age and the second at 4-6 years of age. In addition, young adults (18 years of age or older) born after 1956 who have not been immunized or have not had mumps, should receive at least one dose of MMR vaccine.
Two doses of mumps vaccine are more effective than a single dose: the effectiveness of MMR in preventing mumps is approximately 80% after one dose and 90% after two doses. Because the vaccine is not 100% effective, mumps can occur in people who have been vaccinated. In a community of 400,000 people who received two doses of vaccine, you could still have as many as 40,000 who are susceptible to mumps infection. Recent mumps outbreaks occurring mainly in university students in Halifax, Nova Scotia are thought to be related to a combination of factors:
- susceptible people who received both doses of vaccine but did not develop adequate immunity,
- people who received only one dose of vaccine,
- living/working/socializing in crowded conditions (e.g. college dormitories).
MMR vaccine may take 2-4 weeks for full protection to be achieved. Therefore, during an outbreak, newly-vaccinated people may develop mumps for up to one month after vaccination.
MMR vaccine side-effects do occur, although serious problems are rare: most people do not experience side-effects, and the risks associated with MMR immunization are lower than those of measles, mumps or rubella infection.
Mild Side-effects:
- fever (1/6 people vaccinated),
- mild rash (1/20 people vaccinated),
- swelling of glands in the cheeks or neck (rare).
Moderate Side-effects:
- seizure (jerking or staring) caused by fever (1/3,000 people vaccinated),
- temporary pain and stiffness in the joints (1/4 people vaccinated),
- temporary low platelet count (1/30,000 people vaccinated).
Severe Side-effects:
- serious allergic reaction (< 1/1,000,000),
- deafness, long-term seizures, coma, and brain damage have occurred following vaccination, but happen so rarely that it is unknown whether this is related to MMR vaccine or not.
Measures to limit an outbreak include:
- rapid identification and isolation of suspected cases,
- Identification and vaccination of susceptible people,
- regular handwashing,
- avoiding sharing glasses or utensils,
- covering the mouth and nose when coughing or sneezing,
- staying home when sick.
Sources:
Mumps: Centers for Disease Control and Prevention
