Short-Term School Closures Ineffective for Controlling Influenza Epidemics

Closing schools for less than two weeks during an influenza epidemic has no effect on infection rates, according to a study by researchers at the University of Pittsburgh, RTI International and the Allegheny County Health Department.

The study, published online this week in the Journal of Public Health Management and Practice, was developed from a series of computer simulations that characterize influenza transmission in Allegheny County (Pittsburgh) Pennsylvania.

The findings indicate that schools may need to be closed for at least eight weeks in order to significantly reduce the spread of infection.

Closing schools has been considered and used as strategy to stem or slow the current H1N1 influenza pandemic. Indeed, hundreds of schools across the country have been closed at different periods during 2009 to prevent the spread of infection.

"Since children are more susceptible to most influenza strains than adults, closing schools seems an obvious strategy to slow the spread of flu," said study coauthor Philip C. Cooley, assistant director of bioinformatics and a Fellow at RTI. "However, computer simulations indicate that such closures are ineffective unless they are sustained for at least eight weeks after implementation."

Closing schools quickly at the start of an outbreak was much less effective than keeping them closed continually throughout the epidemic, Cooley said.

According to study authors, short-duration school closures may actually increase infection rates by returning susceptible students back to school in the middle of an epidemic when they are most vulnerable to infection.

The study also found that identifying sick students individually and keeping them from attending school had minimal impact on an epidemic. In addition, there were no significant differences between individual school closures and system-wide closures in mitigating an epidemic.

The study was based on a computer simulation model of Allegheny County, Pa., that represented the county's population, school systems, hospitals, workplaces, households and communities.

The model was developed to evaluate three school-focused strategies for dealing with H1N1 outbreaks: isolating sick children individually at home but leaving the school open, closing the entire school system and closing individual schools.

Simulations were based on the movement of residents each weekday from their households to designated workplaces or schools. To account for the lack of real information about individual's movements, RTI's Geospatial Spatial and Technology Group developed complex synthesized populations of 1.2 million people, including 200,000 school-aged children, more than 500,000 households and nearly 300 schools.

The study is part of the Models of Infectious Disease Agent Study (MIDAS) funded by the National Institutes of Health that has separately funded RTI International and the University of Pittsburgh to conduct vanguard modeling of the spread of infectious diseases and advise health officials.

RTI coauthors of the study include William Wheaton and Diane Wagener, PhD, who is RTI's principal investigator on the MIDAS project.

RTI's MIDAS project team is collaborating with researchers across the nation to answer a number of other major research questions concerning the transmission of influenza. Additional studies will be published in the coming months.