What's driving the spike in mumps cases in U.S.?
01:52 - Source: CNN

Story highlights

Experts say the virus could be spreading from neighboring Arkansas

The outbreaks are not due to a lack of vaccinations

Although vaccination protection wanes over time, it can make complications less likely

CNN  — 

The Texas Department of State Health Services warned this week of multiple ongoing mumps outbreaks. The surge, which includes 221 cases this year, constitutes the highest incidence of mumps in the state in 22 years.

Mumps is a contagious disease caused by a virus that spreads from person to person through saliva and mucus.

“What we’ve seen – as in other parts of the country, (it’s) really just the same thing – a pretty big resurgence in mumps cases over the last six or eight months,” said Chris Van Deusen, spokesman for the state’s health services department. In 2016, Texas experienced 192 mumps cases, he said, primarily in the last few months of the year.

Mumps typically begins with fever, headache, muscle aches, tiredness and loss of appetite lasting a few days, according to the US Centers for Disease Control and Prevention. Most people will have swelling of the salivary glands, causing puffy cheeks and a swollen jaw. Generally, symptoms last at least two days but no more than 10 days.

Because it is caused by a virus, mumps does not respond to antibiotics. Doctors generally recommend bed rest and over-the-counter pain relievers.

“We have largely seen outbreaks in North Texas, so the Dallas-Fort Worth area and some of the surrounding counties,” Van Deusen said, adding that Dallas County has experienced two or three significant outbreaks.

“We’ve had quite a large one with, counting last year and this year, more than 150 cases in Johnson County, which is just south of Fort Worth,” he said. “We’ve certainly seen cases in other areas of the state, but those have been where the largest outbreaks have been centered.”

An outbreak in Johnson County, in particular, included 189 cases spanning last year and this year among children and a couple of college students, he said.

“There have been people who have traveled back and forth between (Johnson County) and Northwest Arkansas, where they’ve been seeing much of the activity, so it seems to be linked to that outbreak,” Van Deusen said.

An outbreak of mumps began in Arkansas in August, explained Dr. Dirk Haselow, Arkansas’ state epidemiologist. Between August and April 13, Arkansas reported 2,930 cases, he said. (Similarly, Washington state (PDF) has been hard hit by the mumps, reporting 611 confirmed and probable cases during 2017.)

“We’ve had less than 500 cases this year,” said Haselow, who believes his state is at the tail end of its outbreak. “Thankfully, the number of cases we’ve had each week decreased recently. We’ve only added 14 cases in the last three weeks.” At the height of the outbreak, nearly 50 cases a day were reported across 35 counties. Today, only four counties are experiencing infections.

As for a possible spread from his state to Texas, Haselow has no doubts.

“Mumps has a long incubation period, as long as 26 days between exposure and symptoms, so people could have been exposed, you know, a little over a month ago, and now you have new cases with that association,” he said.

Across the nation, most mumps cases are occurring among people who have been vaccinated, according to the CDC, and these outbreaks are not due to low vaccination rates. For example, in Texas, 97.6% of kindergarten-age children have received two doses of the measles-mumps-rubella vaccine, Van Deusen said, while 98.7% of seventh-graders have.

The CDC recommends that children get two doses of the MMR vaccine. One dose is considered about 78% effective initially (PDF), and two doses are about 88% effective. So even if you are vaccinated, you need to practice primary prevention.

“Obviously, one of the things you do is avoid people with mumps,” said Infectious disease specialist Dr. William Schaffner, but he noted that this practice is limited in its ability to ward off the mumps for two reasons.

“People can actually spread the mumps virus for several days before they become sick,” he said. The second reason: Mumps also causes subclinical infections.

“That is, I can get infected, but I don’t get sick. Still, I’m capable of passing it on to someone else,” Schaffner said. “That’s a big problem.”

Mumps can cause complications, especially in adults. These include deafness and inflammation of the brain, ovaries, breast tissue or testicles. Occasionally, mumps can cause encephalitis, which in rare cases can lead to death, says the CDC.

There’s a safe way to prevent complications, Schaffner says: the MMR vaccine.

“We say that the vaccine, after 15 years, is about 85% effective,” he said. So the bad news is that 15% of people who have been vaccinated are likely to become ill if they encounter mumps very closely.

“However, the good news is, the complications of mumps seem not to develop,” Schaffner said. People who have been vaccinated are unlikely to get meningitis or inflammation of the ovaries or testes, or partial deafness. “It would appear these complications are not occurring among these individuals who have partial immunity. They get a milder infection.”

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    Those who favor pre-emptive strikes might consider an updated vaccine, he said.

    “Should everyone traveling to Texas get another dose of MMR? We’re not there yet,” Schaffner said, adding that the CDC is not recommending such measures.

    Still, if you’re visiting family in Texas and know that they have the mumps, you might go to your doctor beforehand and request a dose of MMR, he suggested.

    “You may have to pay for it out of pocket,” he said. “How much protection it gives me, I don’t know, but it is a safe and easy thing to do.”

    Each year, the number of mumps cases fluctuates within a range of a couple hundred to a couple thousand cases, according to the CDC. In 2016, 5,311 cases were reported in 46 states and the District of Columbia.