By Susan Scutti CNN

(CNN) -- A county-by-county survey of Washington state conducted by CNN on Wednesday found 400 confirmed and probable cases of mumps since October. Mumps is a contagious disease caused by a virus spread from person to person through saliva and mucus.

Two counties are reporting just one case each, while six counties have multiple cases. King County tops the list at 179 confirmed or probable cases. Spokane County has 158, Tacoma-Pierce County 44, Grant County nine, Snohomish County five, Ferry County three and Thurston and Yakima Counties each with just one.

"It's been a continuous upwards track of new cases. However, until we reach a point where no more vulnerable people are exposed, it may continue to grow," said Dave Johnson, a spokesman for the Washington State Department of Health.

According to Kim Papiuch, spokeswoman for the Spokane Regional Health District, "what we're seeing is expected, especially as we look to other areas that are dealing with outbreaks, like King County." The outbreaks among "partners in Arkansas and other areas of the country" also indicate that the outbreak in Washington is continuing in a typical manner.

Each year, the number of mumps cases fluctuates within a range of a couple hundred to a couple thousand cases, according to Dr. Manisha Patel, a medical officer at the US Centers for Disease Control and Prevention. During 2016, a 'high' year, 46 states and the District of Columbia reported 5,311 total cases but only a handful of states pushed the numbers above average. Arkansas, Iowa, Oklahoma, New York and Illinois each confirmed more than 300 cases.

"Just looking at incubation period and method of transmission, we expect that we're going to still go through a few more waves of the outbreak, so we don't expect cases to necessarily slow down yet," Papiuch said.

Washington state itself has reported 349 confirmed and probable cases of the mumps as of February 1, with plans to update this information Thursday. Papiuch said each county does its own case management and feeds information to the State Department of Health, so updates can be delayed.

According to Johnson, the state department of health is "assisting local health departments with the case investigations" and giving "clinical guidance to healthcare providers about diagnosing and testing for mumps."

"We continue to supplying vaccine to local health departments to be sure there is enough for people who need it," said Johnson. "The best way to control the mumps outbreak is to educate people about how to protect themselves and their families from mumps. The MMR vaccine is our first line of defense."

How to halt an outbreak

Officials urge people to get vaccinated and to take precautions to stop the spread.

The CDC recommends that children get two doses of the MMR vaccine, which protects against measles, mumps and rubella, though it is not 100% effective. The CDC is working closely with the state department of health, according to Patel.

If you suspect someone of having mumps, you should avoid kissing, hugging and other close contact. Anyone feeling sick should contact their health care provider, local health departments or the Family Health Hotline at 1-800-322-2588, Washington health authorities said.

The CDC has received reports of 263 cases of mumps nationwide for the first four weeks of 2017 (PDF).

Mumps typically begins with fever, headache, muscle aches, tiredness and loss of appetite lasting a few days. Most people will then see salivary glands swell, causing puffy cheeks and a swollen jaw. It can take 12 to 25 days to become ill after exposure to the virus. Once symptoms begin they can last from two to 10 days.

Mumps can occasionally cause complications, especially in adults. These include hearing loss 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.

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

Dosage debate

The CDC recommends that children get their first dose of MMR vaccine at 12 to 15 months of age and the second dose at 4 to 6 years old. The alternative MMVR vaccine, which protects against measles, mumps, rubella and varicella (chickenpox), is licensed for use in children between the ages of 12 months and 12 years.

The MMR vaccine effectiveness is 88% with two doses. This means that if 100 vaccinated people are exposed to the mumps, 12 will still become sick. In people who receive just one of the two recommended doses, the vaccine is less effective.

With regard to the current outbreak in Washington, Papiuch noted, "our vaccine efficacy seems to be high, and so our number of cases is representative of the vaccine affording pretty good protection."

In December, the CDC said that most of the individual state outbreaks had been occurring among vaccinated people. Outbreaks in recent years, most notably one involving NHL players in 2014, have spurred debate over the need for a third dose of vaccine.

The Advisory Committee on Immunization Practices -- a panel of medical and public health experts who meet three times a year to offer vaccination guidance for the United States -- has begun the work to consider the recommendation of a third dose of vaccine.

A working group will consider multiple components and data from ongoing effectiveness studies and then present its recommendations to the committee for a vote, Patel said.

"Safety, effectiveness, implementation -- a number of things are considered when a recommendation is put forth," she said, adding that this process will probably take 12 to 18 months.

Before the US mumps vaccination program started in 1967, the CDC received reports of 186,000 cases each year. Since most doctors considered the mumps a typical childhood disease, the actual number of cases was probably much higher. Cases decreased by more than 99% in the US in the years after the vaccination program initially began.

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