Washington state mumps outbreak the worst in the nation in late December

There are 24 confirmed or probable cases of mumps in Spokane County, a sharp increase from a week ago when there were nine. Statewide there were 151 cases, more than the rest of the nation combined for the late December to early January reporting period, according to data from the Centers for Disease Control and Prevention.

During a normal year, there are one or two mumps cases in Spokane County, said Mark Springer, a Spokane County Regional Health District epidemiologist.

“Our health care provider community has stepped up quite a bit,” Springer said. “Because again, this is a fairly rare disease to see in Spokane.”

There were seven confirmed mumps cases Tuesday in the Mead School District, a district spokesman said. In Spokane Public Schools there were eight confirmed cases and three probable cases on Wednesday.

Of the 24 cases, 17 of the people were fully vaccinated, and seven had an unknown vaccination status.

According to Springer, most of the children who contracted mumps were immunized. Although a measles-mumps-rubella vaccine prevents about 88 percent of mumps cases after two doses, it’s possible for someone who has been vaccinated against the disease to get sick.

As for the adults contracting the disease, Springer said it’s harder to tell their immunization history, unless they have immunization documentation.

Statewide there are 151 cases of mumps, according to the Washington Department of Health, with 123 cases in King County. It’s the most severe mumps outbreak in the state in 26 years, according to David Johnson, a Department of Health spokesman.

There were 5,311 reported mumps cases in the U.S. in 2016; 48 of those were in Washington.

Springer said it’s been a decade or more since Spokane County has seen an outbreak of this severity.

The most recent cases diagnosed in Spokane likely originated from a mid-December outbreak. The timing of that outbreak over the holidays allowed the disease to spread.

“There are a lot of social activities associated with Christmas and New Year’s,” Springer said.

It’s unknown if the most recent outbreak in Spokane is connected with the King County cases.

Although mumps is spread through respiratory droplets, it “requires close contact over an extended period of time,” Springer said.

That’s why it’s more common among families, and in places like college dorms. Infection is less likely to occur at work, or in other public spaces like supermarkets or coffee shops, Springer said.

Most likely there will be new mumps cases through February, Springer said.

The current outbreak comes after a smaller outbreak at Whitworth University, which was declared over in early December.

Now, health district employees are mapping where anyone with a confirmed case of mumps may have spent significant amounts of time. Once they identify someone who has a high risk of contracting the disease, the health district sends a monitoring letter. Mumps is contagious for about eight days.

There are between 15 and 20 health district staff working on containing the outbreak.

Kim Papich, Spokane Regional Health District spokeswoman, said the district sends letters to all families and staff at the affected schools, and if enough cases occur, to the entire school district.

“The health district is doing everything in its power to stem the spread of the cases,” she said. “Affected school districts are being really cooperative.”

Staff reporter Rachel Alexander contributed to this report.