Flu season starts in western Canada and drifts east, McMaster study suggests

Climate plays a big role in determing when the flu season starts, according to a team of researchers based out of McMaster University.

Findings will help health officials organize vaccination campaigns, researchers say

Unlike the morning sun, the flu season in Canada rears its head in the west before drifting east, according to a new report out of McMaster University.

The research, released this week in the biological sciences journal Proceedings of the Royal Society B, suggest the start of the winter flu season is sparked by cool temperatures and low humidity in the fall — events that tend to occur earlier in the western provinces.

A team of researchers from McMaster led by Daihai He, now a professor at the Hong Kong Polytechnic University, arrived at these findings by analyzing data on laboratory-confirmed cases of influenza A from across Canada from period spanning from October 1999 to March 2013.

"Each year, the flu season emerged much earlier in the west — in Alberta and British Columbia — and very late in Newfoundland," said He, who spearheaded the study while working on his did post-doctorate work at McMaster.

"The difference could be as much as five weeks," he said.

Their findings indicate that weather patterns can also explain why the start of the flu season can vary from year to year.

"If you know you have low temperatures and humidity in the early autumn, our study suggests that it is more likely that you are going to have an earlier influenza epidemic," said David Earn, an investigator with McMaster's Michael G. DeGroote Institute for Infectious Disease Research who worked the paper, in a news release.

These conclusions, he said, could prove extremely valuable strategy tool in the fight against the spread of the flu each year.

"This is something public health officials might want to consider when determining the timing of a vaccination program."