The 7-year-old boy sat at the edge of a stretcher in the emergency department, looking miserable, as his mother recounted his symptoms to a senior resident physician on duty. Low-grade fever, fatigue, and myalgias prompted rapid SARS-CoV-2 testing at his school. That test, as well as a repeat test at the pediatrician’s office, were negative. A triage protocol in the emergency department prompted a third test, which was also negative.
Dr. Kristina A. Bryant
“Everyone has told me that it’s likely just a different virus,” the mother said. “But then his cheek started to swell. Have you ever seen anything like this?”
The boy turned his head, revealing a diffuse swelling that extended down his right cheek to the angle of his jaw.
“Only in textbooks,” the resident physician responded.
It is a credit to our national immunization program that most practicing clinicians have never actually seen a case of mumps. Before vaccination was introduced in 1967, infection in childhood was nearly universal. Unilateral or bilateral tender swelling of the parotid gland is the typical clinical finding. Low-grade fever, myalgias, decreased appetite, malaise, and headache may precede parotid swelling in some patients. Other patients infected with mumps may have only respiratory symptoms, and some may have no symptoms at all.
Two doses of measles-mumps-rubella vaccine have been recommended for children in the United States since 1989, with the first dose administered at 12-15 months of age. According to data collected through the National Immunization Survey, more than 92% of children in the United States receive at least one dose of measles-mumps-rubella vaccine by 24 months of age. The vaccine is immunogenic, with 94% of recipients developing measurable mumps antibody (range, 89%-97%). The vaccine has been a public health success: Overall, mumps cases declined more than 99% between 1967 and 2005.
But in the mid-2000s, mumps cases started to rise again, with more than 28,000 reported between 2007 and 2019. Annual cases ranged from 229 to 6,369 and while large, localized outbreaks have contributed to peak years, mumps has been reported from all 50 states and the District of Columbia. According to a recently published paper in Pediatrics, nearly a third of these cases occurred in children <18 years of age and most had been appropriately immunized for age.
Of the 9,172 cases reported in children, 5,461 or 60% occurred between 2015 and 2019. Of these, 55% were in boys. While cases occurred in children of all ages, 54% were in children 11-17 years of age, and 33% were in children 5-10 years of age. Non-Hispanic Asian and/or Pacific Islander children accounted for 38% of cases. Only 2% of cases were associated with international travel and were presumed to have been acquired outside the United States
The reason for the increase in mumps cases in recent years is not well understood. Outbreaks in fully immunized college students have prompted concern about poor B-cell memory after vaccination resulting in waning immunity over time. In the past, antibodies against mumps were boosted by exposure to wild-type mumps virus but such exposures have become fortunately rare for most of us. Cases in recently immunized children suggest there is more to the story. Notably, there is a mismatch between the genotype A mumps virus contained in the current MMR and MMRV vaccines and the genotype G virus currently circulating in the United States.
With the onset of the pandemic and implementation of mitigation measures to prevent the spread of COVID-19, circulation of some common respiratory viruses, including respiratory syncytial virus and influenza, was sharply curtailed. Mumps continued to circulate, albeit at reduced levels, with 616 cases reported in 2020. In 2021, 30 states and jurisdictions reported 139 cases through Dec. 1.
Clinicians should suspect mumps in all cases of parotitis, regardless of an individual’s age, vaccination status, or travel history. Laboratory testing is required to distinguish mumps from other infectious and noninfectious causes of parotitis. Infectious causes include gram-positive and gram-negative bacterial infection, as well as other viral infections, including Epstein-Barr virus, coxsackie viruses, parainfluenza, and rarely, influenza. Case reports also describe parotitis coincident with SARS-CoV-2 infection.
When parotitis has been present for 3 days or less, a buccal swab for RT-PCR should be obtained, massaging the parotid gland for 30 seconds before specimen collection. When parotitis has been present for >3 days, a mumps Immunoglobulin M serum antibody should be collected in addition to the buccal swab PCR. A negative IgM does not exclude the possibility of infection, especially in immunized individuals. Mumps is a nationally notifiable disease, and all confirmed and suspect cases should be reported to the state or local health department.
Back in the emergency department, the mother was counseled about the potential diagnosis of mumps and the need for her son to isolate at home for 5 days after the onset of the parotid swelling. She was also educated about potential complications of mumps, including orchitis, aseptic meningitis and encephalitis, and hearing loss. Fortunately, complications are less common in individuals who have been immunized, and orchitis rarely occurs in prepubertal boys.
The resident physician also confirmed that other members of the household had been appropriately immunized for age. While the MMR vaccine does not prevent illness in those already infected with mumps and is not indicated as postexposure prophylaxis, providing vaccine to those not already immunized can protect against future exposures. A third dose of MMR vaccine is only indicated in the setting of an outbreak and when specifically recommended by public health authorities for those deemed to be in a high-risk group. Additional information about mumps is available at www.cdc.gov/mumps/hcp.html#report.
Dr. Bryant is a pediatrician specializing in infectious diseases at the University of Louisville (Ky.) and Norton Children’s Hospital, also in Louisville. She said she had no relevant financial disclosures. Email her at pdnews@mdedge.com.