Public health officials in Nova Scotia say there are now seven confirmed cases of measles in the province, an increase from three cases confirmed in the Halifax area last week.

Dr. Trevor Arnason, medical officer of health for Halifax, the Eastern Shore and West Hants, calls discovery of more cases unsurprising, given how contagious the virus is.

"Measles is very contagious. Measles can be passed from one person to another in a room, or even entering a room that someone with measles left up to two hours prior. It's one of the most contagious diseases we know of," he told CBC News on Thursday. 

"In this case, we were able to identify the locations that were shared between all the individuals who have come down with the illness."

He said it was a "positive sign" that only seven cases have been found and that medical staff have talked to people who came into contact with the infected people. No one has been hospitalized or suffered complications from the measles outbreak, he said. 

Measles

This image from the Centers for Disease Control and Prevention shows an electron microscope image of a measles virus particle. (The Associated Press)

The three cases confirmed last week were linked and the people affected were known to each other. They all live in the Halifax area, but Arnason said they "did travel somewhat within the province." 

Arnason would not identify the affected people, only to say they are young adults. He said health officials are contacting workplaces where the infected people could have spread the measles. 

Risk still low

On Thursday, the Nova Scotia Health Authority said all the current cases are young adults and that the risk to the general public remains low. The authority and said most people are protected from a measles infection because of vaccinations. 

Arnason noted that people vaccinated in the 1970s to 1990s got only one dose, whereas children now get two. He said adults can get that second dose for free from their doctors. 

Measles can have serious complications for some, including infants, pregnant women and those with weakened immune systems. Symptoms of measles include fever, cough, a red blotchy rash and small white spots inside the mouth and throat.

First measles cases since 2008

Arnason said the ongoing investigation of the confirmed cases has included notifying some organizations and businesses so that they can help share information with their staff and clients about measles symptoms. 

"It's important to quickly identify those who have symptoms so that precautions can be taken to prevent the spread of measles and follow up with as many people as possible who may have been exposed," he said. 

Anyone with symptoms of measles is asked to contact their local Public Health office or contact 811 for advice from a registered nurse.  

The cases are the first in Nova Scotia since 2008. Arnason said measles had been eliminated in Nova Scotia, so they think the new cases were "brought in by a traveller," most likely via the U.S..

with files from Dave Irish