Periods of mandatory school closures and other social distancing measures reduced influenza transmission by about one-third in Mexico during the spring 2009 pandemic. The research was carried out by Fogarty scientists and published in PLoS Medicine.
Social distancing interventions can be implemented during unusual infectious diseases outbreaks and include school closings, shuttering of movie theaters and restaurants, and the cancellation of large public gatherings. Mexico implemented a nationwide mandatory school closure policy during an 18-day period in late April and early May 2009.
The study was led by Gerardo Chowell, Ph.D., a Fogarty investigator and faculty member at Arizona State University, Tempe. His team provides the first comprehensive epidemiological description of the age, geographical and severity patterns of the 2009 pandemic in Mexico.
The authors applied mathematical modeling to influenza surveillance data compiled by a large private health system, the Mexican Institute for Social Security, which covers 40 percent of the population.
A three-wave pandemic profile was identified throughout Mexico during 2009. The initial wave occurred in spring in the Mexico City area. A second wave was noted in summer in the southeastern region, with a third wave following in the fall.
The hardest hit were the very young, not the elderly who are typically at high risk for influenza. There were a few cases reported among seniors during the pandemic period, but the most severe influenza-related infections were seen in those 5 to 14 years old and infants.
"We believe this study has implications for improving preparedness plans in future pandemics," said Chowell. Noting that, in a previous influenza pandemic in the 19th century, the majority of deaths occurred two years after the initial wave, he emphasized that "we must remain vigilant and continue to monitor the circulation and health burden of the pandemic A/H1N1 and co-circulating influenza viruses in the coming years."