There has been one recorded case in King County, which is the area around Seattle.
Last year, there were 17 outbreaks and about 350 cases of measles in the U.S.
The source of the outbreak affecting Washington has not been determined. Twenty-six of those suffering from the disease had not been immunized and the vaccination status of four others was unverified.
Thirty confirmed cases have been reported in Clark, while one has been reported in King County.
Washington Gov. Jay Inslee declared a state of emergency over the measles outbreak Friday. 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. For now, public health officials are focused on preventing additional exposure. While it is expected most will not be affected by the outbreak, those who have not been vaccinated against the disease, including infants less than a year old, are at risk.
Before the vaccine, 400 to 500 people died from the measles each year, 50,000 people were hospitalized and 4,000 people developed brain swelling that can cause deafness, he said.
The disease was declared eliminated in the United States in 2000 but has since made a comeback that is tied to imported cases and the rise of the anti-vaccine movement. No cases related to the Clark County outbreak have been reported in the province, but B.C.'s vaccination rate now sits below the 95 per cent necessary to achieve herd immunity.
Measles is highly infectious and spreads through the air by coughing and sneezing, as well as respiratory secretions. The measles vaccine consists of two shots, one given by age 2 and the second usually between ages 4 and 6. Symptoms include cough, runny nose, sore throat, fever and blotchy skin rashes.
Two doses of the vaccine in childhood are 97 percent effective and provide lifetime immunity.
"Because measles is contagious before people realize they are sick, those who are not vaccinated may spread the disease without knowing".