Mumps Cases Spike; 2016 Total Is Highest in a Decade

Mumps cases nationally have hit 249 in the past 4 weeks, nearly 4 times normal levels, according to data published in the December 2 issue of the Morbidity and Mortality Weekly Report.

The recent outbreaks have pushed the nation's 2016 total to 3832 preliminary cases, the largest number of cases in 10 years, and three times last year's total of 1088.

Manisha Patel, MD, from the Centers for Disease Control and Prevention's (CDC's) Division of Viral Diseases, told Medscape Medical News that the high monthly numbers follow the pattern in a high-incidence year, but they may also reflect that states are trying to get their year-end numbers in.

As of November 5, 45 states and the District of Columbia had reported mumps cases this year. Six states (Arkansas, Iowa, Indiana, Illinois, Massachusetts, and Oklahoma) have reported more than 100 cases, according to the CDC.

Arkansas has the highest total by far, at 1305 cases this year, which is twice Iowa's 645, the next highest state total.

Three states are responsible for most of the total of 48 cases reported in the latest week: Arkansas (22 cases), Oklahoma (11), and New York (12).

According to the Arkansas Department of Health website, the department is currently responding to an active outbreak of mumps in the northwest part of the state. Kids with vaccine exemptions in Arkansas schools where there have been infections are required to stay home from school for 26 days unless they get the vaccines.

Arkansas' cases are mostly centered in grade schools and high schools, but nationally, the cases primarily have been spread among the clusters of students at universities. The mumps virus is spread through saliva and mucus by coughing, sneezing, kissing, or other direct contact.

New York is experiencing an outbreak at the State University of New York (SUNY) New Paltz campus. On December 9, the New York State Department of Health (NYSDOH) reported 63 "confirmed or probable cases" associated with the SUNY New Paltz location since October, and more are being investigated.

The NYSDOH, together with the Ulster County Health Department and SUNY New Paltz, held a vaccination clinic December 13 and 14 at the university.

One dose of the measles, mumps, and rubella (MMR) vaccine is considered 78% effective in preventing mumps, and two doses are 88% effective, according to the CDC.

NYSDOH recommends that students get a third dose of the MMR vaccine and is providing it for free. Medscape Medical News previously reported that the third dose may be beneficial in outbreaks.

"There is increasing evidence that a third dose of the MMR vaccine will help raise immunity among the students who have not yet been exposed, and help prevent the further spread of mumps on the campus," NYS Health Commissioner Howard Zucker, MD, said in a university news release. "We are also urging students to wash their hands regularly, avoid contact with people who may be sick, and immediately notify their healthcare provider if they suspect they are sick. Students who are ill should stay home from classes and social events."

The CDC says adults born before 1957 are considered immune to mumps after 1 vaccination, but children should get two doses, and adults born in 1957 or later should have a second dose if they are in a college or university, work in a healthcare facility, or plan to travel internationally.

Dr Patel said the CDC is working with the Advisory Committee on Immunization Practices, a panel of US health experts who meet three times a year to establish vaccination guidance, to gather and analyze data on whether a third MMR dose should be recommended, and for whom.

The CDC is also working with public health experts on the epidemiology of mumps and how waning immunity contributes to these outbreaks.

"It's important to remember that two doses of MMR can reduce your risk of getting mumps and reduce the risk of severe mumps, and also reduce the risk of transmitting to others," Dr Patel said.

Before the US mumps vaccination program started in 1967, the CDC received reports of 186,000 cases each year.

The authors and Dr Patel have disclosed no relevant financial relationships.

Morb Mortal Wkly Rep. Published online December 1, 2016. Full text

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