Last year was the worst in the past decade for mumps infections in the United States, with nearly three times as many cases nationwide as in 2015, according to data from the CDC.
As of Dec. 3, 2016, more than 4,000 cases of provisionally diagnosed mumps had been reported across 46 states and Washington, D.C., compared with 1,329 cases in 2015 and 229 in 2012. Arkansas, Illinois, Indiana, Iowa, Massachusetts, New York, and Oklahoma all reported more than 100 cases this year. While most patients recover in a few weeks, mumps can produce serious complications, such as deafness and inflammation of the testicles, brain, or ovaries.
Mumps is especially becoming a problem for college campuses: The University of Missouri saw 128 confirmed or probable cases of mumps since this past fall, while SUNY New Paltz confirmed 33 cases on campus.
But "oddly enough," Dina Fine Maron reports for Scientific American, "most mumps patients said they had received their two recommended doses of the combined measles-mumps-rubella (MMR) vaccine." In Arkansas, the state with the largest outbreak in 2016, about 70 percent of mumps patients self-reported they had been fully vaccinated against the disease.
The explanation may be that the MMR vaccine begins to wane about a decade after inoculation, explained Paul Offit, a professor at the Children's Hospital of Philadelphia. Traditional vaccine schedules give children their second dose of the mumps vaccine between ages 4 and 6—meaning that, by the time they reach college, the effects of the vaccine have begun to fade. Crowded on-campus living conditions and frequent social gatherings create ideal conditions for the disease to spread.
This winter, CDC's Advisory Committee on Immunization Practices will consider recommending a third dose of the MMR vaccine to increase the length of inoculation. The effectiveness of the third vaccination has not been established, however, and CDC is working with college campuses to assess how well emergency third-dose campaigns have worked during recent outbreaks.
But while the surge in mumps cases may be due to an inadequate vaccination schedule, the disease also could just be in the midst of a natural rise, said Janell Routh, a medical officer with the CDC. "We know generally that mumps cases wax and wane over years," she said. Routh added that the virus has not mutated in a way that makes the MMR vaccine less effective (Maron, Scientific American, 12/16/16; Korn, Wall Street Journal, 12/5/16; Frellick, Medscape, 12/15/16).
What population health will look like in 2017
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