Parents be warned – children who have not received both doses of measles vaccine could be forced to miss three weeks of school if a classmate contracts the highly contagious disease.

So far, eight students in Vancouver have been diagnosed with measles, forcing another six uninfected but unvaccinated children to take time off.

Medical health officer Réka Gustafson said the lengthy quarantine is necessary to protect fellow students, and that measles can take up to 19 days to incubate.

"We tend not to do this very often because we are aware of the impact of missing school on a child," Gustafson said.

"Measles is the most contagious disease we know of. It's a nasty disease to get."

If a child is diagnosed early, within three days, then fellow unimmunized students have the option of getting a last-minute vaccination and returning to class.

But detection can be difficult, Gustafson said, because early measles symptoms are similar to cold and flu symptoms.

"By the time measles declares itself, the window for intervention has passed," Gustafson said.

The illness begins with a fever, runny nose and cough. Days later, a rash appears around the face, which then spreads to the chest and limbs. The eyes may also be red and sensitive to light.

A total of 42 cases have been diagnosed across B.C. in the past month, including 18 in Vancouver. It is the first measles outbreak reported in the province since 1997.

The spread of measles is slow in B.C., Gustafson said, because most children receive both necessary doses of the vaccine before their second birthday.

Anyone unsure of their own or their children's immunization history is advised to check with their family physician.

"Now is a very good time to make sure that you got both doses," Gustafson said.

Different strains identified

The centre has identified two separate strains of the virus – one believed to have been brought in by out-of-country visitors during February or early March, the other brought home by a British Columbian man returning from India.

There are currently cases reported in every health authority in B.C., the majority diagnosed in the Fraser Valley and Metro Vancouver areas.

The initial outbreak reported on March 30 consisted of 10 confirmed and four suspected cases. Eight of the cases came from a single household of unvaccinated members.

Measles can also lead to serious health problems. One in every 1,000 infected suffers an inflammation of the brain, which can lead to convulsions, deafness or permanent mental disability. One in every 3,000 cases can result in death.

More information on measles is available at the BC Centre for Disease Control website.