There are early signals that measles — one of the world's most contagious but preventable diseases — may be spreading in parts of Canada. Andrew Chang breaks down the way the virus attacks the body and what makes it so contagious. »»» Subscribe to CBC News to watch more videos: http://bit.ly/1RreYWS Connect with CBC News Online: For breaking news, video, audio and in-depth coverage: http://bit.ly/1Z0m6iX Follow CBC News on TikTok: https://bit.ly/3TnHioe Follow CBC News on Twitter: http://bit.ly/1sA5P9H Find CBC News on Facebook: http://bit.ly/1WjG36m Follow CBC News on Instagram: http://bit.ly/1Z0iE7O Subscribe to CBC News on Snapchat: https://bit.ly/3leaWsr Download the CBC News app for iOS: http://apple.co/25mpsUz Download the CBC News app for Android: http://bit.ly/1XxuozZ »»»»»»»»»»»»»»»»»» For more than 80 years, CBC News has been the source Canadians turn to, to keep them informed about their communities, their country and their world. Through regional and national programming on multiple platforms, including CBC Television, CBC News Network, CBC Radio, CBCNews.ca, mobile and on-demand, CBC News and its internationally recognized team of award-winning journalists deliver the breaking stories, the issues, the analyses and the personalities that matter to Canadians.