SAINT JOHN, N.B. -- A measles outbreak in southern New Brunswick has spread to a second high school.

The province's chief medical officer, Dr. Jennifer Russell, confirmed Saturday that the latest confirmed case is someone who either works or studies at Hampton High School, northeast of Saint John.

As of Saturday, there were 12 confirmed cases of the highly contagious disease in the Saint John area, all of them linked to New Brunswick's first confirmed case -- a person who travelled outside the province before showing up at Saint John Regional Hospital in late May.

Russell said the other cases involve people exposed either at the emergency department at Saint John Regional or at Kennebecasis Valley High School.

The latest case is linked to a previously confirmed case at Kennebecasis Valley High School, she said.

On Saturday, health officials said a special clinic would be set up to immunize those at Hampton High School who may have been exposed.

"The fact that they're all directly linked is reassuring, in the sense that we know how everybody contracted measles," Russell said in an interview Saturday.

A dose of vaccine is the best way to protect people who have been exposed to the disease, Russell said. But that vaccination must be administered within 72 hours, regardless of previous immunization history.

On Friday, the province issued a warning to those who use taxis in the Saint John area, saying someone with a confirmed case of measles travelled repeatedly by taxi on May 22, 24, 25 and 26, using Vet's Taxi Ltd.

The cab company operates 68 vehicles, and health officials don't know which one was used by the infected person.

People using the same cab afterward could have been exposed to the virus up to two hours later, Russell said, noting the disease is spread by "respiratory droplets" that can remain in the air for that long.

She said anyone who may have been in those cabs won't be offered the vaccine because too much time has passed.

"It wouldn't be effective outside that window of 72 hours," she said.

"All we can do is make those people aware and to watch for symptoms. That's the best advice we can give in terms of protecting the public from further transmission.... Having the public know that information is really important."

About 9,000 doses of the vaccine have been distributed to deal with the outbreak, but many people in the province are having trouble getting a preventative shot.

The New Brunswick Pharmacists' Association says local pharmacists have run out of the vaccine and likely won't get more until July.

Late last week, U.S. health officials reported 971 measles cases so far this year, the highest tally in 27 years.

They say overall vaccination rates have remained fairly high, but outbreaks have been reported in communities where parents have refused recommended shots.

Early symptoms of the measles may include fever, cough, red eyes, runny nose or tiny white spots in the mouth. Within three to seven days, a red, blotchy rash will appear, first on the face and then spreading to the body, arms and legs.

Provincial health officials say if these symptoms appear, it is important for patients to isolate themselves from others and contact the province's Telecare system by dialling 8-1-1.

Russell says those suspecting an infection should not go to a clinic, physician's office or emergency room.

Most people in Canada are already protected from measles, thanks to two doses of vaccine they typically receive as children. In New Brunswick, the vaccine that protects against measles, mumps, rubella and varicella is offered free of charge for babies aged 12 months and 18 months.

Health officials in New Brunswick say they need to count 40 consecutive days without new cases before they can consider the current outbreak over.

-- By Michael MacDonald in Halifax