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(CNN) —  

As of Monday, there are 36 confirmed cases of measles in the state of Washington – an outbreak that has already prompted Gov. Jay Inslee to declare a state of emergency.

“Measles is a highly contagious infectious disease that can be fatal in small children,” Inslee said in his proclamation on Friday, adding that these cases create “an extreme public health risk that may quickly spread to other counties.”

There were 35 cases of the measles in Clark County, which sits on the state’s southern border, just across the Columbia River from Portland, Oregon. Officials said 31 of the cases involved people who have not had a measles immunization; the other four are not verified. Of the 35 cases, 25 are children between age 1 and 10. There are also 11 suspected cases in Clark County.

There is also one case in King County, which includes Seattle. While the King County website says the patient, a man in his 50s, is a “suspected case,” the governor said in a news release it is a confirmed case of measles.

In a health alert from King County, it was said the man had recently traveled to Clark County.

Inslee’s proclamation allows agencies and departments to use state resources and “do everything reasonably possible to assist affected areas.”

Meanwhile, the state legislature has introduced a bill that would ban personal exemptions for the measles vaccine. The proposed legislation was sent to the House Health Care & Wellness Committee.

A news release on the governor’s website says the Washington State Department of Health, or DOH, has implemented an infectious disease incident management structure so it can manage the public health aspects of the outbreak through investigations and lab testing.

The Washington Military Department, the release says, is organizing resources to assist the DOH and local officials in easing the effects on people, property and infrastructure.

Last week, a person infected with measles attended a Portland Trail Blazers home game in Oregon amid the outbreak. Contagious people also went to Portland International Airport, as well as to hospitals, schools, stores, churches and restaurants across Washington’s Clark County and the two-state region, county officials said.

Most patients with symptoms should call first

Measles is a contagious virus that spreads through the air through coughing and sneezing. Symptoms such as high fever, rash all over the body, stuffy nose and red eyes typically disappear without treatment within two or three weeks. One or two of every 1,000 children who get measles will die from complications, according to the US Centers for Disease Control and Prevention.

In 1978, the CDC set a goal to eliminate measles from the United States by 1982. Measles was declared eliminated – defined by absence of continuous disease transmission for greater than 12 months – from the United States in 2000.

But there has been a recent rise in unvaccinated children. The proportion of children receiving no vaccine doses by 2 years old rose from 0.9% among those born in 2011 to 1.3% among those born in 2015, the CDC reported in October.

In Clark County, Washington, where the current outbreak is occurring, 7.9% of children entering kindergarten had vaccine exemptions during the 2017-18 school year, according to the Washington State Department of Health. During the same school year, 7.5% of children in all grades in the county had vaccine exemptions.

“That’s a high number,” CNN Chief Medical Correspondent, Dr. Sanjay Gupta said Monday. “Once you start to dip below 95% vaccination you start to lose the herd immunity. I have immunity because I got the vaccine but I’m also protecting people around me due to the herd. Once you start to drop down as low as you see there (in Clark County), you lose that herd immunity and that’s also part of the concern,” he explained.

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The CDC recommends people get the measles, mumps and rubella vaccine to protect against those viruses. The typical recommendations are that children should get two doses of MMR vaccine, the first between 12 to 15 months of age and the second between 4 and 6 years old.

CNN’s Pierre Meilhan, Artemis Moshtaghian, Faith Karimi, Debra Goldschmidt, Ben Tinker and Kevin Flower contributed to this report.

Correction: This article and an accompanying video previously included a photograph of a child with a rash linked to a vaccination. The image has been removed.