"Once it sets into a community, the likelihood of it getting beyond that community or more widespread within that community is high, especially when vaccination rates are low", Mou told CBS News.
With an outbreak of measles centered in Clark County, Gov. Jay Inslee Friday announced a state of emergency, calling the situation an "extreme public health risk that may quickly spread to other counties".
The CDC says that typically individuals get measles overseas in areas where immunization rates are low, and then spread the illness in pockets of unvaccinated people.
Officials say the man had recently traveled to Vancouver, Washington, where a measles outbreak is happening, but it's not clear if that's where he was infected. As of yesterday, there are 25 confirmed cases in Clark County and one confirmed case in King County.
"So we can expect to continue to see cases related to this outbreak for many weeks and probably many months".
Officials have identified several locations in Auburn, Kent and Covington, including two crowded high school basketball games at Kentlake High School on January 10 and 12, visited by the infected person last week.
With measles apparently making a comeback in the U.S., Seattle Children's Hospital pediatrician Douglas J. Opel said that preventive steps need to be made urgently.
A doctor's assistant brings a tray with a vaccine against measles, rubella, mumps and chicken pox prior to the vaccination of an infant on February 26, 2015 in Berlin, Germany. One dose of the measles vaccine is about 93 percent effective at preventing measles.
The virus, spread by coughing or sneezing, can remain in the air for up to two hours in an isolated space.
Every time an unvaccinated person who has been exposed to measles goes out in public, "it starts that clock over again", Armstrong said.
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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. The CDC says in the province children receive two doses of measles-containing vaccine during routine immunization. The virus can lead to pneumonia (infection of the lungs) and encephalitis (swelling of the brain).
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Woods narrowly made the cut, but surged on the final day with five birdies in his final eight holes to get into the top 20. Woods also captured the last of his majors at the US Open on this course in 2008. "I'll be ready in a couple weeks".