Health officials have issued a public alert after two passengers on a flight from Beijing to Vancouver over the weekend tested positive for measles.

Vancouver Coastal Health said the passengers were aboard Air China flight CA991, which arrived on Saturday, and both would have been infectious during the trip.

Any passengers from flight CA991 who aren’t up-to-date for their measles immunizations are urged to contact their family doctor or visit a walk-in clinic and get vaccinated as soon as possible.

Health officials said despite the disease being rare, it isn’t surprising that cases have now popped up in B.C.

“We’ve seen cases in cases in California, we’ve seen cases in Ontario and we do get occasional cases of measles imported to Vancouver,” Coastal Health’s Dr. Reka Gustafson said. “We are a very international city, we have people coming from all over the world.”

Fortunately, Gustafson said, the majority of British Columbians are immune.

Measles is a serious disease that can cause complications including deafness and brain damage, and it kills one in every 3,000 Canadians who catch it, according to health officials.

It’s also highly infectious and can be spread through the air. Vancouver Coastal Health warns that sufferers are contagious even before they exhibit the classic red rash and fever.

Early symptoms are cold-like, and include coughing and a runny nose.

Anyone who develops a rash or fever is advised to see their doctor, but urged to call ahead.

“Tell them that you think you or your child may have measles. This will allow your doctor to take precautions to protect other patients,” the authority said in a statement.

People born before 1957 are considered immune to measles and don’t need a vaccine. People born between 1957 and 1970 should have one dose of vaccine and everyone born after should have two.