A modeling study of school closure to reduce influenza transmission: A case study of an influenza A (H1N1) outbreak in a private Thai school

The A/H1N1 influenza pandemic has been in the spotlight since the virus was first detected in Mexico in early 2009. To prevent the repetition of the 1918 influenza pandemic, the global response to this pandemic has been strong. In Thailand and in many other countries, schools have been a major source of outbreaks, which then spreads to the general population. Understanding the dynamics of school outbreaks and the impact of disease intervention in school settings is crucial for the effective mitigation of a pandemic. Using data from outbreaks in School G, a private school in Bangkok where detailed epidemiological data were collected, we estimated the basic reproduction number (R0)(R0) to be 3.58 [95% confidence interval: 2.88 to 4.28]. We then modeled outbreaks in school settings with Susceptible-Exposed-Infectious-Recovered (SEIR) equations and tested various interventions such as school closure and student screenings. We found that closing the school on the date with the peak number of daily incidences usually appeared to be effective in preventing further outbreaks. However, if the school was closed too early, subsequent cases would appear after reopening. With no intervention, the number of total cases reaches 83%. Individual student screenings appeared to reduce the number of total cases by up to 40%. In a situation in which the widespread outbreak of a mild disease is unavoidable and in which the goal is to slowly reach sufficient herd immunity while minimizing the number of cases, closing the school at the predicted date with the peak number of daily incidences and screening for respiratory symptoms appear to be the most appropriate intervention methods.