Mumps Outbreaks: Why and Who is Most at Risk?
Darin Seehafer
Darin Seehafer
Sr. Director, Center for Vaccines and Emerging Infectious Diseases

State health officials reported in mid-April that mumps cases have hit a 20-year high in Texas, especially affecting visitors to popular beaches over spring break. Meanwhile, in nearby Arkansas, health officials are investigating more than 2,900 cases, many in the large immigrant community from the Marshall Islands.

Already in Texas, the number of mumps cases this year has hit 221 – the most in that state since 234 cases in 1994. In Arkansas, the state health department reports that 90-95 percent of school-aged children and 30-40 percent of adults involved in a recent outbreak had been fully immunized but that the vaccine “is not perfect.” Two MMR doses are about 88 percent effective in preventing mumps.

A community of Marshall Islanders in Arkansas has been particularly hit by the mumps outbreak, accounting for about 60 percent of the state’s 2,220 reported cases since August. About 12,000 Marshallese live in the northwest section of the state. State officials are investigating why so many Marshallese have been infected despite widespread immunizations.

Higher education incubators

South Padre Island, which hosts vacationing students from Texas and other schools throughout the country, has reported possible exposures after students returned to campus and symptoms – which can take weeks to develop – appeared.

It’s not unusual for colleges and universities to be hotspots of transmissible diseases like mumps. Universities hit hard over the past few years are in Missouri, New York, Massachusetts, Washington DC, Arkansas, Illinois, Missouri, Iowa, California, Tennessee and other states. Relatively closed and densely populated environments easily expose students to the virus, which is spread through saliva or mucus, especially from sharing food or drinks, or kissing. Not surprisingly, fraternity and sorority parties as well as local bars are the biggest culprits.

Mumps map

Source: Morbidity and Mortality Weekly Report (MMWR), Notifiable Diseases and Mortality Tables

But what about childhood vaccinations?

Although they usually received one or two MMRs (measles, mumps, rubella) as children, the immunogenicity of those vaccinations may have started to fade by the time kids reach college age, making them more vulnerable. Researchers do not believe, however, the virus has mutated since the vaccine was first made available in the 1960s – the main genotype has remained the same for years.

The U.S. Advisory Committee on Immunization Practices (ACIP) is considering whether a third MMR vaccine should be added to the country’s childhood vaccine schedule. Recommendations are not expected until February 2018.

ACIP’s working group on this topic is especially concerned about administering that third dose without simultaneously providing unnecessary doses for measles and rubella. ACIP currently considers extra doses of MMR to be “not ideal” and even ineffective. Still, health officials in Arkansas and other states have recommended a third MMR dose as a control measure for college students during outbreaks

…the immunogenicity of those vaccinations may have started to fade by the time kids reach college age

What’s next?

Health officials are keeping an eye on the trend: In 2012, only 229 cases were reported, while last year, that number edged closer to 6,000 cases reported to CDC. This year, by March 25th, however, nearly 2,000 cases had already been reported to CDC.

While mumps in children and teenagers can be unpleasant – swollen salivary glands (the tell-tale puffy face), fever, headache, loss of appetite and a feeling of tenderness – it can become more serious in adults. Some cases can lead to such serious complications as deafness, encephalitis, meningitis and inflammation of the testicles, ovaries and breasts.

Mumps is always circulating in the population, but now may be time to recommend all adults get a mumps booster to help thwart such large outbreaks from occurring.

**Preliminary data reported to CDC. Mumps outbreaks are not reportable.
* Case count is preliminary and subject to change.
**Cases as of March 25, 2017. Case count is preliminary and subject to change.

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