The Washington state’s Department of Health has reported a total of 404 confirmed cases of mumps since October 2016. The outbreak is likely to continue to grow, and health officials are urging any one who is eligible to get vaccinated.
Mumps is a contagious disease caused by the mumps virus and is spread between people through saliva and mucus. Symptoms typically include fever, muscle pain, and general malaise. One of the defining characteristics of mumps is the swelling of one or both parotid salivary glands, giving affected people the look of a swollen face.
In Washington state, the counties with the most cases of mumps include King County (176 cases), Spokane County (165 cases), and Tacoma-Pierce County (45 cases). Five other counties have also reported mumps cases, but the numbers there are still in the single digit.
Mumps is considered to be an uncommon disease in the US ever since the introduction of the MMR (Mumps, measles, rubella) vaccine. Before the vaccine, around 186,000 cases of mumps were reported annually. Since the MMR vaccine program was started in 1967, the US has seen a 99 percent decrease in the number of mumps cases.
Although the vaccine is highly effective, cases of mumps still appear occasionally because not everyone can get vaccinated (due to pre-existing health conditions, for example). In addition, with the rise of the anti-vaccine movement, some people are deliberately opting for no vaccinations. As such, the number of mumps cases are still within the expected range.
"It's been a continuous upwards track of new cases. However, until we reach a point where no more vulnerable people are exposed, it may continue to grow," said Dave Johnson, a spokesman for the Washington State Department of Health.
"Just looking at incubation period and method of transmission, we expect that we're going to still go through a few more waves of the outbreak, so we don't expect cases to necessarily slow down yet," said Kim Papich, spokeswoman for the Spokane Regional Health District.
Of note, within the last 15 years, 2006 and 2016 had the highest record of confirmed mumps cases, with over 6,500 cases and over 5,300 cases, respectively. The reason for the spike in mumps cases then and now? Researchers aren’t sure just yet. But fortunately, they can confirm that it’s not a new strain of mumps that’s evading the vaccines. "We've had more than a dozen samples from our outbreak sequenced and determined that, no, it's not an unusual strain, it's the same strain the United States had for 30 years and the same strain involved in all these other outbreaks,” said Dr. Dirk Haselow, an epidemiologist at Arkansas, which reported a high number of mumps cases in 2016.
What do health officials recommend as the best way to prevent mumps? Vaccinate, vaccinate, vaccinate.
"We continue to supplying vaccine to local health departments to be sure there is enough for people who need it," said Johnson. "The best way to control the mumps outbreak is to educate people about how to protect themselves and their families from mumps. The MMR vaccine is our first line of defense."
The CDC recommends that children get 2 doses of the MMR vaccine, once at 12-15 months, and again at 4-6 years old. Vaccination protects these children directly, and also helps to indirectly protect other people who can’t be vaccinated due to health contraindications.