title: Why is school closed today? Unplanned K-12 school closures in the United States, 2011-2013.
abstract: BACKGROUND
  We describe characteristics of unplanned school closures (USCs) in the United States over two consecutive academic years during a non-pandemic period to provide context for implementation of school closures during a pandemic.
  
  
  METHODS
  From August 1, 2011 through June 30, 2013, daily systematic internet searches were conducted for publicly announced USCs lasting ≥ 1 day. The reason for closure and the closure dates were recorded. Information on school characteristics was obtained from the National Center for Education Statistics.
  
  
  RESULTS
  During the two-year study period, 20,723 USCs were identified affecting 27,066,426 students. Common causes of closure included weather (79%), natural disasters (14%), and problems with school buildings or utilities (4%). Only 771 (4%) USCs lasted ≥ 4 school days. Illness was the cause of 212 (1%) USCs; of these, 126 (59%) were related to respiratory illnesses and showed seasonal variation with peaks in February 2012 and January 2013.
  
  
  CONCLUSIONS
  USCs are common events resulting in missed school days for millions of students. Illness causes few USCs compared with weather and natural disasters. Few communities have experience with prolonged closures for illness.
authors.affiliation: Division of Global Migration and Quarantine, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America.
authors.forename: Karen K
authors.initials: KK
authors.lastname: Wong
authors.affiliation: Division of Global Migration and Quarantine, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America.
authors.forename: Jianrong
authors.initials: J
authors.lastname: Shi
authors.affiliation: Division of Global Migration and Quarantine, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America.
authors.forename: Hongjiang
authors.initials: H
authors.lastname: Gao
authors.affiliation: Division of Global Migration and Quarantine, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America.
authors.forename: Yenlik A
authors.initials: YA
authors.lastname: Zheteyeva
authors.affiliation: Chenega Government Consulting, Chesapeake, Virginia, United States of America.
authors.forename: Kimberly
authors.initials: K
authors.lastname: Lane
authors.affiliation: Division of Global Migration and Quarantine, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America.
authors.forename: Daphne
authors.initials: D
authors.lastname: Copeland
authors.affiliation: Oak Ridge Associated Universities, Oak Ridge, Tennessee, United States of America.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Hendricks
authors.affiliation: Oak Ridge Associated Universities, Oak Ridge, Tennessee, United States of America.
authors.forename: LaFrancis
authors.initials: L
authors.lastname: McMurray
authors.affiliation: Oak Ridge Associated Universities, Oak Ridge, Tennessee, United States of America.
authors.forename: Kellye
authors.initials: K
authors.lastname: Sliger
authors.affiliation: Division of Global Migration and Quarantine, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America.
authors.forename: Jeanette J
authors.initials: JJ
authors.lastname: Rainey
authors.affiliation: Division of Global Migration and Quarantine, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America.
authors.forename: Amra
authors.initials: A
authors.lastname: Uzicanin
mesh_terms: D004190:Disasters; D006801:Humans; D012574:Schools / Q000706:statistics & numerical data*; D012621:Seasons; D018582:Sick Leave; D013334:Students / Q000706:statistics & numerical data; D014481:United States; D014887:Weather