What is mumps?

Mumps is an acute viral infection spread primarily by coughing and sneezing. Some people with mumps are almost asymptomatic, meaning that they don't have any noticeable symptoms, or have a mild infection that resembles any other upper respiratory tract infection. In "classic mumps," the most common symptoms are fever, headache and swollen salivary glands.

Generally, it's a more serious illness in adults than in children. Most people who get mumps do not experience serious complications, though occasionally encephalitis (inflammation of the brain), mastitis or oophoritis (inflammation of the breast or ovaries), and orchitis (inflammation of the testes) may occur. These problems can lead to permanent hearing loss and male infertility.

Wasn't mumps previously eliminated by a vaccine?

The mumps vaccine was introduced in 1967 and recommended for universal use in 1977, causing a significant decline in the US. However, this year, the Midwest has seen an outbreak of mumps.

According to the U.S. Center for Disease Control and Prevention, since 2001 an annual average of 265 mumps cases has been reported nationwide. But as of May 4, more than 2,869 cases have been reported in 13 states -- more than 10 times the national average. Of these, 1,552 are confirmed, probable or suspected cases in Iowa.

So far, there are no cases that have been associated with the Midwest outbreak in the Bay Area and state of California. However, it is likely that some cases of mumps will develop in California, and therefore it is important to understand the condition and be able to recognize its symptoms.

Why are we seeing a significant outbreak of mumps?

Vaccination is not 100 percent effective. One dose of the vaccine results in about 80 percent immunity; a second dose results in about 90 percent immunity. That means that in a 100 percent vaccinated population, 10 percent of the people still won't be immune. That's generally acceptable and results in only sporadic cases.

However, when you have a group of people living together in close quarters for an extended period of time, such as in the military or in a college dorm, there is a higher probability of infection. This appears to be the case in the Midwest, where it began on a college campus and most of the people were between 18 and 25 years old. If the population hadn't been vaccinated, there would be many more than 1,100 new cases.

We know that the "serotype" of the outbreak virus is serotype G, the same one that has been circulating in the United Kingdom. Do we think mumps was brought here from the UK?

We don't really know what caused the recent mumps outbreak. The UK has had recent outbreaks of mumps, though we do not know if this is linked to the cases here in the US.

How is mumps spread?

You can contract mumps from someone actually coughing in your face, but you can also get it from droplets in the room. You can also touch a surface that an infected person recently touched, such as toys, public areas, etc. and infect yourself by touching your eyes, nose or mouth.

After being exposed to mumps, how long does it take to develop symptoms?

The usual incubation period from the time you are exposed to the virus until the time you have symptoms ranges from 16 to 18 days, but the shortest is 11 or 12 days, and it can be up to 25 days. Most people are contagious from about three days before to nine days after the swelling of the glands.

What should parents who might be concerned about their children getting the mumps do?

Parents should make sure that all their children of any age are fully immunized for mumps and other vaccine-preventable diseases.


Reviewed by health care specialists at UCSF Medical Center.

This information is for educational purposes only and is not intended to replace the advice of your doctor or health care provider. We encourage you to discuss with your doctor any questions or concerns you may have.

Related Information

UCSF Clinics & Centers

Infectious Disease

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