Here are the key facts on this highly contagious virus.

By Kathleen Felton
Updated March 20, 2019

It seems like we keep hearing about mumps outbreaks lately, particularly at universities. So far in 2019, 18 states have reported cases of mumps, according to the Centers for Disease Control and Prevention (CDC).The classic signs of mumps are puffy cheeks and a swollen jaw, symptoms triggered by tender salivary glands. In children, the illness is generally mild—but in adults, it can lead to severe complications. And while many people are vaccinated against mumps, they can still get sick. Here, five things you should know about the disease.

The vaccine doesn't work for everyone

In the U.S., most patients who get the MMRV vaccine (against measles, mumps, rubella, and varicella) are innoculated with the Jeryl Lynn strain of the mumps virus, says Aileen Marty, MD, a professor of infectious diseases at Florida International University. (It's named after Jeryl Hilleman, the daughter of the doctor who developed the mumps vaccine.) Studies show that this strain offers protection for 95% of people at best, leaving about 5% of people vulnerable. "That's why we give two doses," she says. "The first dose at 12 to 15 months, and again at 4 to 6 years of age." But even with the standard two doses, some patients "may not produce the quality or quantity of antibodies needed for life-long protection," she explains.

You may not know you have mumps

People typically experience non-specific symptoms at first, like muscle pain, headache, and a low-grade fever, says Dr. Marty. "Then, in about a day or two, they'll start to notice the swelling of the parotid glands—glands in the cheek," she says. "Usually both [cheeks] are affected, although one side usually swells up bigger than the other." Patients may also experience pain, difficulty swallowing, loss of appetite, and a general sense of being unwell.

But about 30% of patients don't develop any symptoms at all, which is part of the reason the virus can spread so quickly, as those people unwittingly infect others. "Think of them as 'Typhoid Mary' for the mumps virus," says Dr. Marty.

It's highly contagious

Another reason mumps is tough to avoid: "Infected people shed the virus long before they start to have symptoms," says Dr. Marty. In other words, if your BFF contracts mumps, she may not realize she's ill until two days after she became contagious. "So you don't really know who to protect yourself from." The virus is spread through saliva, so you could contract it from a cough, sneeze, or just talking to an infected person. To protect yourself, it's best to avoid sharing items such as cups or utensils, and to wash your hands frequently (and for a full 20 seconds).

Mumps can become quite serious

While most people recover from mumps within a few weeks, it's possible for the disease to worsen. Complications can include hearing loss, testicular inflammation (orchitis), inflammation of the ovaries (oophoritis)—even inflammation of the brain and spinal cord. "This virus loves brain tissue," says Dr. Marty. "As many as 50% to 60% of infected people experience a high rise in white blood cells in their cerebrospinal fluid, which can sometimes lead to someone manifesting symptoms of meningitis." In rare cases, patients could also suffer seizures or paralysis.

If you think you have it, see your doc immediately

While there's no treatment for the disease itself, your primary care physician can treat your symptoms and monitor you for complications. For example, Dr. Marty explains that your doctor may prescribe acetaminophen a nonsteroidal anti-inflammatory drug to reduce fever or pain caused by swollen salivary glands. Warm or cold packs can also help relieve discomfort, she adds. "And if the patient develops meningitis or has persistent vomiting, we may provide IV fluids."

This article was originally published on April 28, 2016 and has been updated for accuracy.

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