The state of emergency directs Washington state agencies and departments to use their resources to assist affected areas in order to respond and recover. Most of the confirmed cases - 21 - were with children between 1 and 10 years old.
Of the 31 cases in Clark County, 27 cases involve unimmunized people.
Health department officials have connected 27 of the Clark County measles cases to non-immunized people while four cases remain unverified.
But there has been a recent rise in unvaccinated children.
Clark County now has 31 confirmed cases of measles and eight suspected cases as of January 26.
Locations and venues include Portland International Airport, at the Moda Center during a Portland Trail Blazers basketball game, an Amazon Locker location and stores such as Costco and Ikea.
With the measles outbreak in the Clark County area of Washington state growing, now up to 30 confirmed cases and several suspected, Gov. Jay Inslee declared a state of emergency on Friday.
Health officials warn he came in contact with hundreds of people.
People who choose not to vaccinate their children are underestimating the dangers of the illness, said Melnick, who himself had measles as a child, before the vaccine was commonplace. "Two doses of measles, mumps and rubella (MMR) vaccine provides over 95 percent protection against measles and that protection is long lasting".
Last week, a person infected with measles attended a Portland Trail Blazers home game in OR amid the outbreak. "Fortunately, the measles vaccine is very effective".
Measles is a contagious virus that spreads through the air through coughing and sneezing. One dose of the measles vaccine is about 93 percent effective at preventing measles.
Those who may have been exposed should watch for early symptoms of fever and malaise and then a rash starting on the head and moving down the body.
To avoid infecting others, Clark County Public Health urges anyone who believes they may have been exposed to measles or are experiencing symptoms of the disease to call a health-care provider, to discuss being evaluated before going to a doctor.