Annals of Internal Medicine
February 7, 2012; 156 (3)
http://www.annals.org/content/current

Original Research
Effects of School Closure on Incidence of Pandemic Influenza in Alberta, Canada
David J.D. Earn, Daihai He, Mark B. Loeb, Kevin Fonseca, Bonita E. Lee, and Jonathan Dushoff
Ann Intern Med February 7, 2012 156:173-181;

Controversy exists as to whether schools should close during influenza epidemics. Researchers developed a mathematical model of H1N1 influenza transmission in Alberta, Canada, by using virologic data, census data, climate records, and school calendars. The model suggests that school closure reduced influenza transmission among schoolchildren by more than 50%, attenuating the first peak of the H1N1 influenza epidemic. Reopening of schools initiated the second peak. Closing schools may be an effective strategy to slow the spread of influenza during epidemics.

Editorials
Getting Schooled: School Closure, Age Distribution, and Pandemic Mitigation
David N. Fisman
Ann Intern Med February 7, 2012 156:238-240;

Excerpt
Despite the gains in antimicrobial therapy and vaccines that have come in the past 100 years (1), epidemics and pandemics (synchronized, global epidemics) remain an important source of morbidity, mortality, and costs in high-, middle-, and low-income countries. Epidemics can be thought of as self-perpetuating, exponential growth processes; because infections are communicable, the more cases you have, the more cases you will get, as long as the population contains susceptible persons to infect.

Epidemiologists refer to the key index of this type of growth as the reproductive number of an infectious disease—the number of new (incident) cases created by each old (prevalent) case before the prevalent case recovers (2). Reproductive numbers are the product of 3 core components: how infectious a person is, the duration of infectiousness of a person, and how many contacts that person has. Epidemic mitigation strategies that seek to reduce the latter component of the reproductive number (contact between infectious and susceptible persons) are often referred to as social-distancing measures.

Social-distancing measures may include closing schools, suspending religious services, and canceling large public gatherings. A famous study in contrasts with respect to the implementation of social distancing for influenza pandemic control occurred in St. Louis and Philadelphia during the severe influenza A(H1N1) pandemic in 1918 to 1919 (3). Authorities in Philadelphia declined to impose social-distancing measures (including, famously, not canceling a parade through the center of the city that drew large crowds) until the epidemic was severe. In contrast, St. Louis proactively and aggressively restricted religious and social gatherings and closed schools early in its epidemic, and the effect of influenza seems to have been greatly mitigated (3). Whether the divergent courses of St. Louis and Philadelphia were attributable to social-distancing measures or whether the willingness to implement such measures reflected …