A mumps outbreak in Arkansas continues to grow at an alarming rate. As of December 8th, the total number of suspected and confirmed cases of mumps in Arkansas now stands at 1,898. In Arkansas alone, the number of cases reported exceeds that of the national total for 2015. Of great concern in this outbreak, 90% to 95% of school-aged children and 30% to 40% of adults involved in the outbreak have been fully immunized . As of December 6, eleven counties are involved, they are: Benton, Carroll, Clark, Conway, Faulkner, Garland, Howard, Madison, Pulaski, Washington and Yell .
What is Mumps?
Mumps is an infectious viral disease that is transmitted through saliva or mucus, from the mouth, nose, or throat. Common symptoms include fever, headache, muscle aches, and tiredness. The infection is characterized by the puffy cheeks and swollen jaw that it causes. Symptoms typically appear 16-18 days after infection, and most people recover completely within several weeks. Outbreaks are more common in crowded environments, such as college campuses, and with behaviors that result in sharing saliva occur, such as in a preschool where toys are shared .
The MMR (measles, mumps, and rubella) vaccine has been exceptional at reducing the number of mumps cases in the U.S. Since the pre-vaccine era, there has been a more than 99% decrease in mumps cases in the United States . Overall, two doses of the MMR vaccine are about 88% effective at preventing mumps infection. The Centers for Disease Control and Prevention (CDC) attributes outbreaks of mumps to be a result of a combination of factors - including the effectiveness of the vaccine, lack of previous exposure to wild-type virus, and the intensity of the exposure (such as a college campus) coupled with behaviors or factors that increase the risk of transmission .
What happened in this outbreak?
The majority of cases in the ongoing outbreak in Arkansas have been among school-aged children. In response to the outbreak, Arkansas Department of Health is requiring students with vaccine exemptions for the MMR vaccine to stay home from school for 26 days from the date of exposure and until the outbreak has ended .
A state epidemiologist, Dirk Haselow, MD, PhD, stated that the specific strain of mumps seen in the current outbreak in Arkansas is one of the most genetically distinct from the strain used to create the vaccine. There is speculation that the mumps virus may have evolved enough to make the vaccine less effective , just as we see with the influenza vaccine being a bad fit for a particular flu season.
The outbreak in Arkansas is not a singular event. As of November 5th, six other states have reported more than 100 cases this year: Arkansas, Iowa, Indiana, Illinois, Massachusetts and Oklahoma . There have also been reported outbreaks across the U.S. this year, including the University of Missouri, Yale University, SUNY- New Paltz, and in King County of Washington [5,6,7, 8]. To prevent transmission, the CDC recommends staying away from other people if you are infected, avoiding sharing drinks or eating utensils, disinfecting toys and commonly touched surfaces often, and using general hygiene practices such as washing hands often and covering your mouth and nose with a tissue when you cough or sneeze . In addition to these methods, vaccination remains, by far, the most effective way to prevent transmission and infection.