A 16-month-old girl was brought to the ED by her parents for evaluation of swelling under her left ear that began earlier that day. She was well-developed and well-nourished with no significant past medical history and up-to-date vaccinations. While in the ED, the patient vomited.
The patient's mother reported that the child had a fever the previous week and a recent upper respiratory infection. Her parents denied any recent travel or sick contacts.
On examination, the patient was crying but was consolable by her parents. Her vital signs were BP, 130/60 mm Hg (elevated for age because of crying); heart rate, 138 (normal for age); respirations, 22; SpO2, 100% on room air; temperature, 99° F (37.2° C); and weight, 9.8 kg (21 lb, 9.7 oz). The physical examination was significant for left-sided facial swelling at the line of the jaw without extension into the soft tissue of the neck. The mass was not fluctuant and was without induration. The patient also presented with rhinorrhea. She was able to breathe and swallow without difficulty. The physical examination was negative for signs of trauma, sublingual edema, or buccal edema.
A mumps IgM antibody titer was drawn but results were not available before the patient was discharged home. The patient had received her first MMR dose on schedule 4 months ago and was not yet due for her second dose.
Diagnosis and outcome
The differential diagnosis included infected lymph node, branchial cleft cyst, mastoiditis, Epstein-Barr virus, cytomegalovirus, parainfluenza viruses, influenza A virus, lymphocytic choriomeningitis virus, coxsackievirus, HIV, nontuberculosis mycobacterium, Gram-positive bacterial infection, and mumps.
The patient received 147.2 mg of acetaminophen, 98 mg of ibuprofen, and 2 mg of ondansetron in the ED to manage her symptoms and was discharged home. Five days later, the clinical diagnosis was confirmed by a positive mumps IgM antibody titer of 2.64 IV (1.21 IV or greater is positive for mumps). The patient was diagnosed with infectious parotitis, also called mumps. The mother was notified and advised to contact the child's pediatrician to set up an appointment for discussion and further evaluation or intervention.
Mumps is a vaccine-preventable viral disease spread through contact with infected respiratory droplets (Figure 1). Although the disease usually is mild, in rare cases it can lead to serious complications. Data from the CDC indicate that the number of cases of mumps in the United States has been increasing, from 229 in 2012 to 6,366 in 2016 and more than 5,600 cases (preliminary figures) in 2017.1 The increasing incidence is due to a failure to maintain herd immunity and regional clustering of nonmedical vaccine exemptions. In addition, clinicians should not rule out mumps in a case of parotid swelling in a partially vaccinated child.
Mumps characteristically causes an acute onset of unilateral or bilateral painful parotitis that presents 2 to 3 weeks after initial exposure to the virus and lasts at least 2 days.2 However, patients may not always have this key symptom. Clinical symptoms are present in 60% to 70% of patients, and 95% of patients with clinical symptoms present with parotitis, but a third of unvaccinated patients who are infected with mumps are asymptomatic.3-5 Mumps often is accompanied by respiratory symptoms, a low-grade fever, or a headache.
Postpubertal males and females can develop orchitis or oophoritis.2,3 In some cases, these complications can result in infertility. Other uncommon but serious symptoms include aseptic meningitis, spontaneous abortion, myocarditis, nephritis, encephalitis, and pancreatitis.2 Epididymoorchitis is the most common of these complications and occurs in 15% to 30% of cases involving postpubertal males.3
The mumps virus is neurotropic and half of infections affect the central nervous system, frequently asymptomatically. Meningitis occurs in 5% to 10% of patients.2 Mumps also is one of the most common causes of unilateral acquired sensorineural deafness, a rare symptom that occurs in 1 in 20,000 patients.3
Consider mumps in any patient with sudden onset of parotitis that lasts at least 2 days coupled with fever, respiratory symptoms, anorexia, malaise, or a headache. If mumps is suspected, immediately collect oral or buccal swab samples for real-time reverse transcription-polymerase chain reaction (PCR) testing. Urine samples are not as useful because they may not be positive for the virus for at least 4 days after symptom onset. An oral sample is obtained by first massaging the parotid gland area for 30 seconds before swabbing the area surrounding the Stensen duct.6
In most cases, a mumps IgM antibody titer should be drawn. A positive IgM antibody titer result is an index value greater than 1.2 IV. However, if a patient has already been given the MMR vaccine, serological tests may be difficult to interpret.7
Some patients who have been vaccinated may never have a detectable mumps antibody response.7 Additionally, the antibody response may not be present until up to 5 days after symptom onset. In patients with negative antibody tests but presentation strongly suspicious for mumps, confirmation with real-time reverse transcription-PCR tests may be necessary. PCR testing is especially important at the beginning of a mumps outbreak, as it is more sensitive than IgM detection.8 Timing is key, as the ability of the real-time reverse transcription-PCR test to detect mumps virus RNA significantly decreases 2 days after symptom onset.7
Mumps generally resolves within a few weeks and no specific antiviral therapy exists to treat it. Patients should be given antipyretics and analgesics to manage their fever and pain as needed.3
Most patients with mumps do not need hospital admission. The severity of mumps infection increases with the patient's age. Complications that may require hospitalization are much more common among adults, and men have a higher rate of complications than women.9 Patients may need hospitalization if they develop a serious complication such as pancreatitis. Patients who begin to experience dyspnea and are at risk for airway obstruction from laryngeal edema, a rare but life-threatening complication, should be hospitalized after an emergency airway is established.10
The Advisory Committee on Immunization Practices' basic schedule for the MMR vaccine is to administer the first dose to patients at age 12 to 15 months, with the second dose following at age 4 to 6 years.11 The minimum interval between doses is 4 weeks. Typically, children should be age 12 months before their first vaccination. An exception to this rule is if the child is traveling internationally. These children can receive their first vaccine as early as age 6 months but must later receive two more doses, at age 12 months and a second dose at least 4 weeks later. Any teenager or adult who does not have evidence of immunity should receive two doses of the MMR vaccine separated by 4 weeks. The first dose of the MMR vaccine is estimated to prevent 64% to 66% of mumps cases with the second dose preventing 83% to 88% of cases.12
Herd immunity is a measure of population scale immunity. The infection of one patient is not an isolated event: that patient can threaten the health of patients who are not immunized, including patients who are too young to be vaccinated and those who are unable to be vaccinated due to a compromised immune system. Vaccinating as many people as possible reduces the potential breeding grounds for microbes and reduces the incidence of transmittable disease.13
The herd immunity threshold for mumps has been estimated at 88% to 92%.9 The most recent data obtained by the CDC for the 2016-2017 school year suggest that the median vaccination coverage in kindergartners after two doses of MMR in the United States is 94%.14 Although this number may sound encouraging, individual states vary widely in their immunization rates. CDC reports of vaccination coverage among children in kindergarten in the United States for the 2016-2017 school year show that coverage varies from 87.3% in Colorado to 99.4% in Mississippi.14 An explanation for this discrepancy between states is nonmedical exemptions—typically parents who refuse to have their children vaccinated because of cultural or religious beliefs. The 2014-2015 school year had a national median percentage of nonmedical exemptions of 1.5% compared with 1.6% in the 2015-2016 school year.14,15 State exemption rates were lowest in states where obtaining an exemption was difficult, and vice versa.16 This wide variation across states is also reflected within states. In Arizona, rates of nonmedical exemptions vary across schools, from 0% to 68%.17 Affluent schools with a higher proportion of white students and a lower prevalence of reduced or free lunches tend to have more students with nonmedical exemptions.18 Although the overall vaccination coverage for MMR in the United States may seem promising, individual school, county, and statewide deficits point toward significant vulnerabilities.
The failure to maintain herd immunity and the regional clustering of nonmedical vaccine exemptions can explain the increasing incidence of mumps. This recent rise in incidence is concerning and directly calls into question the ability to eradicate or prevent outbreaks of this disease.
Any patient presenting with parotitis should be tested for mumps. Clinicians should talk to parents to address their concerns about vaccine safety and explain the benefits of vaccination. If current trends continue, and nonmedical exemption rates are increasingly geographically and socially clustered, herd immunity will be threatened, allowing for subsequent outbreaks of this virus.
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6. Centers for Disease Control. Mumps. Specimen collection, storage, and shipment. www.cdc.gov/mumps/lab/specimen-collect.html
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14. Seither R, Calhoun K, Street EJ, et al. Vaccination coverage for selected vaccines, exemption rates, and provisional enrollment among children in kindergarten—United States, 2016–17 school year. MMWR Morb Mortal Wkly Rep
15. Hill HA, Elam-Evans LD, Yankey D, et al. National, state, and selected local area vaccination coverage among children aged 19–35 months—United States, 2014. MMWR Morb Mortal Wkly Rep
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17. Birnbaum MS, Jacobs ET, Ralston-King J, Ernst KC. Correlates of high vaccination exemption rates among kindergartens. Vaccine
18. Wang E, Clymer J, Davis-Hayes C, Buttenheim A. Nonmedical exemptions from school immunization requirements: a systematic review. Am J Public Health