A measles outbreak in New Brunswick is set to push Canada's annual case count to the highest it's been in five years, highlighting how infectious the disease is and how low vaccination rates have allowed it to take hold, says an immunologist.

There are 43 cases in the province, as of Friday, all in health Zone 3, which includes Fredericton and parts of the Upper Saint John River Valley area, according to the Department of Health.

That's a 72 per cent increase in the three weeks since Public Healt…