The measles vaccine is very effective.
The source of the outbreak affecting Washington has not been determined.
But measles is still a big problem in other parts of the world, wrote the Los Angeles Times.
Around 88 per cent of children in the province have been sufficiently vaccinated against the disease.
There have been 30 recorded cases of the infectious disease in the state's Clark County - just north of Portland - in January.More news: Eating breakfast 'not a good strategy' for weight loss
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.
The B.C. Centre for Disease Control is warning the public after measles outbreaks in areas of Washington State in the U.S. Officials said an unvaccinated female toddler was infected with the virus, which she likely contracted on an global trip to an area that was in the midst of a measles outbreak.
The outbreak is in an anti-vaccination hotspot near Portland, Ore., according to CBS News. The measles vaccine consists of two shots, one given by age 2 and the second usually between ages 4 and 6.
A person is considered immune and is unlikely to get measles if they were born before January 1, 1957, or have received two doses of the MMR (Measles, Mumps and Rubella) vaccine or have a lab test confirming immunity.
Both Washington and OR allow vaccine exemptions for personal and philosophical reasons. Researchers called nearby Portland a "hot spot" for infections due to a high rate of non-medical exemptions from vaccines, according to The Washington Post.More news: Iran face Japan in Asian Cup semifinals
Before the measles vaccination program began in the U.S.in 1963, about 3 to 4 million people in the USA got measles every year. People are contagious with measles for up to four days before and up to four days after the rash appears.
The virus, spread by coughing or sneezing, can remain in the air for up to two hours in an isolated space.
Earlier this week, authorities were successful in identifying several people who had been exposed but were not sick yet.
"Some people say, 'Why would you get vaccinated for something that is no worse than a cold?'" says Leman.
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, Lindquist said. Serious complications such pneumonia and brain infections can arise from the disease in some cases.More news: Samsung Galaxy S10 and Galaxy S10