Montreal has seen 106 cases of whooping cough so far this year, 65 more than at the same time in 2011. The outbreak is quickly spreading across the province.
"It's a highly contagious disease. It spreads through sneezing and coughing and the droplets in the air," said Alexandra Kossowski of the Montreal public health department.
About 80 per cent of the cases in the province this year are in children under 15.
Pediatricians say it all has to do with not getting the right vaccinations. Watch CBC Montreal's report above.