A growing measles outbreak in the Pacific Northwest is spreading fear among many parents. Washington state has declared a public health emergency.

There are now 35 cases in Clark County alone, and there are more than 50 places in Washington confirmed as a "public exposure location" where a person with measles may have exposed others include retail outlets, schools, churches, and grocery stores.

Measles has an infection rate of 90 percent for anyone exposed and not immunized with no visible symptoms for weeks.

Measles are not just uncomfortable – it can be deadly. Studies show almost 30 percent of children younger than five who get the measles will have to be hospitalized, reports CBS News correspondent Jamie Yuccas. Parents are concerned, including Miranda Smith, a mother of three. 

"It's their lives on the line, honestly, if they're not vaccinated and something like this happens, then what am I going to do to save them?" Smith said.

If children get their measles vaccine, they are 95 percent protected. Washington state has introduced legislation to remove the personal vaccination exemption, but it's already facing opposition from some parents who feel the bill takes away their freedom.

The 35 confirmed cases in Washington state prompted Gov. Jay Inslee to declare a state of emergency.

"This can be a serious disease, and you need to get on top of these things quickly in order to prevent really significant spread," Inslee said.

Eighteen states including Washington allow parents to decide not to vaccinate their children due to moral, personal, or other beliefs. There were nearly 350 measles cases recorded last year in 26 states and the District of Columbia, the second greatest number since the disease was eliminated in 2000.

New York state is facing its worst outbreak in decades, with more than 200 cases. 

"It's very hard to change people's minds, especially when you're talking about the health of their children," said Blima Marcus, a nurse practitioner in New York.

She is working to combat misinformation that claims vaccines cause cancer, diabetes and autism – all disproven by the CDC. She said the anti-vaccination pamphlet has been distributed throughout Brooklyn's ultra-Orthodox Jewish community where 62 children have contracted the disease.

"I think that percentage is higher in the Orthodox communities due to all of the propaganda and fear tactics. There are so many pieces of misinformation. Some outright lies, that when put all together, reveal a very terrifying picture of vaccination," Marcus said.

The virus is spread through the air and lingers. If one sick child coughs in a room and leaves, another unvaccinated person can still be exposed hours later. Officials now worry the virus will spread to other large metropolitan areas.

"What types of things are you doing to contain it?" Yuccas asked Inslee.

"We're having our children stay home for a number of days, we're asking people actually to be diagnosed in their homes and not actually at the doctor's office because that can infect people in the office," he responded.  

Learn more about vaccines for children on the CDC's website