Japan makes a good model for studying influenza in schools because it closely monitors school absenteeism due to flu, requires testing for the flu virus in students who become ill, and has a track record of instituting partial or complete school closures during outbreaks. However, Brownstein cautions that the scenarios might play out differently in the U.S. than they would in Japan, mainly because students here aren't required to be tested for influenza as they are in Japan, so it's less certain whether they actually have the flu. Also, the vaccination status of students in this study was unknown.

Last spring, during the early days of the H1N1 influenza pandemic, the CDC recommended first a 7-day school closure, then a 14-day closure after appearance of the first suspected case. Later, as more became known about the extent of community spread and disease severity, the CDC changed the recommendation to advise against school closure unless absentee rates interfered with school function. CDC's current guidelines (cdc/h1n1flu/schools/schoolguidance.htm, 10/21/09) don't provide a specific algorithm, but state that "the decision to selectively dismiss a school should be made locally," in conjunction with local and state health officials, "and should balance the risks of keeping the students in school with the social disruption that school dismissal can cause." When the decision is made to dismiss students, CDC recommends doing so for 5 to 7 calendar days.

Source: Children's Hospital Boston