Closing schools works to slow the spread of flu during pandemics, a study of infection patterns in Alberta suggests.

The study in Tuesday's issue of the Annals of Internal Medicine analyzed data on H1N1 infections in the province during the 2009 pandemic.

School-age children fuelled the spread of pandemic H1N1, researchers say. (Pat Roque/Associated Press)

"School-age children were fundamentally important drivers of [pandemic H1N1] transmission in 2009," the study's lead author, mathematics and statistics Prof. David Earn of McMaster University in Hamilton and his co-authors concluded.

"We suggest that school closures [either local or regional] should be seriously considered if a pandemic occurs during the school year."

When the infectious disease researchers plotted lab-confirmed H1N1 cases on a graph, they could see a huge drop in incidence when schools closed for the summer.

"Using state-of-the-art modelling, we then demonstrated that transmission was reduced by at least 50 per cent," Earn said.

The model also showed that a large drop in temperature seemed to influence a spike in H1N1 cases throughout the province, but the weather changes were less important than closing school for the summer.

Schools in Alberta happened to close for the summer as the first wave of H1N1 infections happened, but the observations suggest that closing all schools could affect the course of future epidemics, the researchers said.

They acknowledged that social disruptions from closing schools also need to be taken into consideration. During the pandemic, public health authorities recommended against school closures.

While other provinces tightened criteria to test for respiratory viruses when the first wave of the pandemic grew in intensity, Alberta did not, which gave the researchers higher-quality data to model.

The study was funded by the Canadian Institutes of Health Research, the Natural Sciences and Engineering Research Council of Canada, the Public Health Agency of Canada and McMaster's Michael G. DeGroote Institute for Infectious Disease Research.