School closures slow spread of H1N1

[img_inline align=”right” src=”http://padnws01.mcmaster.ca/images/davidearn.jpg” caption=”David Earn, a professor in the Department of Mathematics and Statistics, has found that, since school-age children are important drives of H1N1 transmission, closing elementary and secondary schools can help slow the disease’s spread. File photo. “]Closing elementary and secondary schools can help slow the spread of infectious
disease and should be considered as a control measure during pandemic outbreaks,
according to a McMaster-led study.

Using high-quality data about the incidence of influenza infections in Alberta during the
2009 H1N1 flu pandemic, the researchers show that when schools closed for the
summer, the transmission of infection from person to person was sharply reduced.

“Our study demonstrates that school-age children were important drivers of H1N1
transmission in 2009,” said David Earn, lead author of the study published in Annals of
Internal Medicine. Earn is professor in the Department of Mathematics and Statistics and
member of McMaster's Michael G. DeGroote Institute for Infectious Disease Research
(IIDR).

Alberta was the only Canadian province to continue extensive virologic testing
throughout the first wave and continuously to the middle of the second wave of the
2009 pandemic, allowing researchers to identify the causes of changes in incidence as
the pandemic progressed.

“The data we obtained were so good that our plots immediately revealed a huge drop in
incidence when schools were closed for the summer,” said Earn. “Using state-of-the-art
modeling, we then demonstrated that transmission was reduced by at least 50 per
cent.”

The model also indicates that seasonal changes in weather significantly affected
influenza transmission, but that they were much less important than school closures.

“Our study emphasizes the value of gathering data consistently throughout an
outbreak,” said Earn. “For example, in Ontario they imposed testing restrictions on June
11, before schools had closed. We couldn't possibly have done this analysis based on
other parts of Canada.”

Earn and colleagues intend to continue to encourage policy makers to collect data
through the course of an infectious disease outbreak. Only by swabbing large numbers
of people throughout a pandemic, he said, can the effects of various changes in
behavior or control strategies be shown.

He added that this work will help policy makers make the hard decision of whether or
not to close schools during a pandemic outbreak.

“This strongly suggests that closing schools as a preventative measure is a strategy
worth seriously thinking about. The next time a disease like SARS or the 1918 flu
emerges, this paper will give policy makers more confidence that closing schools is
likely to significantly reduce the rate of transmission.”

The study also involved McMaster investigators Jonathan Dushoff, associate professor of
biology, and Mark Loeb, professor and division director of infectious diseases for the
Michael G. DeGroote School of Medicine, who are also members of the IIDR.

The study received funding from 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.
Computing resources for simulations were provided by Compute Canada's SHARCNET.