Thousands of people, mostly children, in the U.S., Canada, and Mexico have contracted the vaccine-preventable disease this year.

An Ontario infant born prematurely and infected with measles has died in the first fatality of a growing provincial outbreak. Health officials say the baby contracted measles before birth and that the mother was unvaccinated.

A Canadian infant who was born prematurely and had measles has died, officials said Thursday without confirming a cause of death, raising heightened concern about the virus's resurgence. "While measles may have been a contributing factor in both the premature birth and death,