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
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.
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.
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