Roughly 100 cases of the measles have been reported in the Fraser Valley east of Vancouver, prompting health officials to warn that cases have begun spreading outside of the previous school and religious groups where they first appeared.

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A red blotchy rash begins to appear on the face three to seven days after the start of symptoms. (U.S. Centre for Disease Control and Prevention)

Chief Medical Health Officer Dr. Paul Van Buynder says only one nine-year-old girl has been admitted to hospital so far, but about 80 new cases have also been reported in the general populations of the two Fraser Valley municipalities of Chilliwack and Agassiz.

Previously dozens of cases had been reported at a Christian School in Chilliwack with a low vaccination rate. That school has been temporarily closed.

"We respect the beliefs of religious groups and we understand they're not going to get vaccinated because of their belief system," said Van Buynder.

"What's disappointing is that the broader population has many people who are susceptible and are at risk. We need to get people to understand that measles infection is a great risk and these vaccines are very safe and very important for protection"

Warning covers Eastern Fraser Valley

The health district says its warning includes all of Fraser Valley East, including Abbotsford, Mission, Chilliwack, Agassiz, Harrison Hot Springs and Hope.

Arrangements are being made to distribute increased measles vaccines to doctors and pharmacies in the area.

Children under the age of five are most at risk of serious complications, and Van Buynder says they should be vaccinated right away.

Special vaccination clinics in Chilliwack and Agassiz are being organized for early next week and their locations will be available on Fraser Health's website.

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The measles virus is passed through airborne droplets and direct personal contact. (U.S. Centres for Disease Control and Prevention)

Van Buynder is asking anyone with symptoms to isolate themselves at home.

“It is not necessary to attend a medical centre for testing to confirm measles during an outbreak unless you are quite sick," he said.

"We know there are measles circulating and laboratory confirmation is not necessary."

Van Buynder says people who are very sick should get to the doctor, but only after warning them that they are coming.

What are the symptoms of measles?

Symptoms of measles may develop seven to 21 days after exposure to an infected person.

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Pregnant women should avoid the antigenic vaccine, but can seek protection with immunoglobulins, Dr. Meena Dawar said. (CBC)

Symptoms include a high fever, runny nose, cough, drowsiness, irritability and red eyes. Small white spots may appear in the mouth and throat.

A red blotchy rash begins to appear on the face three to seven days after the start of symptoms, then spreads down the body to the arms and legs. This rash usually lasts four to seven days.

Symptoms generally last from one to two weeks.

READ: Fraser Health public service announcement on outbreak

With files from Emily Elias