title: A primary school outbreak of pandemic 2009 influenza A (H1N1) in China.
abstract: BACKGROUND
  We investigated the first known outbreak of pandemic 2009 influenza A (H1N1) at a primary school in China.
  
  
  OBJECTIVE
  To describe epidemiologic findings, identify risk factors associated with 2009 H1N1 illness, and inform national policy including school outbreak control and surveillance strategies.
  
  
  METHODS
  We conducted retrospective case finding by reviewing the school's absentee log and retrieving medical records. Enhanced surveillance was implemented by requiring physicians to report any influenza-like illness (ILI) cases to public health authorities. A case-control study was conducted to detect potential risk factors for 2009 H1N1 illness. A questionnaire was administered to 50 confirmed cases and 197 age-, gender-, and location-matched controls randomly selected from student and population registries.
  
  
  RESULTS
  The attack rate was 4% (50/1314), and children from all grades were affected. When compared with controls, confirmed cases were more likely to have been exposed to persons with respiratory illness either in the home or classroom within 7 days of symptom onset (OR, 4.5, 95% CI: 1.9-10.7). No cases reported travel or contact with persons who had traveled outside of the country.
  
  
  CONCLUSIONS
  Findings in this outbreak investigation, including risk of illness associated with contacting persons with respiratory illness, are consistent with those reported by others for seasonal influenza and 2009 H1N1 outbreaks in school. The outbreak confirmed that community-level transmission of 2009 H1N1 virus was occurring in China and helped lead to changes in the national pandemic policy from containment to mitigation.
authors.affiliation: Office for Disease Control and Emergency Response, Chinese Center for Disease Control and Prevention, Beijing, China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Huai
authors.forename: Jinyan
authors.initials: J
authors.lastname: Lin
authors.forename: Jay K
authors.initials: JK
authors.lastname: Varma
authors.forename: Zhibin
authors.initials: Z
authors.lastname: Peng
authors.forename: Jianfeng
authors.initials: J
authors.lastname: He
authors.forename: Chen
authors.initials: C
authors.lastname: Cheng
authors.forename: Haojie
authors.initials: H
authors.lastname: Zhong
authors.forename: Yuansheng
authors.initials: Y
authors.lastname: Chen
authors.forename: Yingdong
authors.initials: Y
authors.lastname: Zheng
authors.forename: Yuan
authors.initials: Y
authors.lastname: Luo
authors.forename: Wenjia
authors.initials: W
authors.lastname: Liang
authors.forename: Xiaoling
authors.initials: X
authors.lastname: Wu
authors.forename: Zhenyu
authors.initials: Z
authors.lastname: Huang
authors.forename: Jeffrey
authors.initials: J
authors.lastname: McFarland
authors.forename: Zijian
authors.initials: Z
authors.lastname: Feng
authors.forename: Timothy M
authors.initials: TM
authors.lastname: Uyeki
authors.forename: Hongjie
authors.initials: H
authors.lastname: Yu
mesh_terms: D000293:Adolescent; D017677:Age Distribution; D016022:Case-Control Studies; D002648:Child; D002681:China / Q000453:epidemiology; D016358:Contact Tracing; D004196:Disease Outbreaks; D005260:Female; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000302:isolation & purification*; D007251:Influenza, Human / Q000453:epidemiology* / Q000821:virology*; D008297:Male; D012189:Retrospective Studies; D012307:Risk Factors; D012574:Schools; D011795:Surveys and Questionnaires
references.citation: PLoS One. 2008;3(12):e4005
references.pmid: 19104659
references.citation: Lancet Infect Dis. 2007 Apr;7(4):257-65
references.pmid: 17376383
references.citation: Euro Surveill. 2009 Aug 20;14(33):
references.pmid: 19712642
references.citation: Emerg Infect Dis. 2006 Jan;12(1):81-7
references.pmid: 16494722
references.citation: Lancet Infect Dis. 2009 Aug;9(8):473-81
references.pmid: 19628172
references.citation: Euro Surveill. 2009 Jul 09;14(27):
references.pmid: 19589330
references.citation: MMWR Morb Mortal Wkly Rep. 2009 Apr 24;58(15):400-2
references.pmid: 19390508
references.citation: Am J Epidemiol. 1980 Jan;111(1):23-30
references.pmid: 7352457
references.citation: Pediatr Infect Dis J. 2004 Jul;23(7):675-7
references.pmid: 15247610
references.citation: N Engl J Med. 2009 Jun 18;360(25):2605-15
references.pmid: 19423869
references.citation: MMWR Morb Mortal Wkly Rep. 2009 May 8;58(17):470-2
references.pmid: 19444151
references.citation: BMC Public Health. 2008 Feb 14;8:61
references.pmid: 18275603
references.citation: Public Health Rep. 1982 Jan-Feb;97(1):66-72
references.pmid: 7058264
references.citation: Emerg Infect Dis. 2009 Sep;15(9):1418-22
references.pmid: 19788809
references.citation: Clin Infect Dis. 1999 Feb;28(2):200-4
references.pmid: 10064226
references.citation: Euro Surveill. 2009 Jul 09;14(27):
references.pmid: 19589328
references.citation: Emerg Infect Dis. 2008 Oct;14(10):1660-2
references.pmid: 18826841
references.citation: Epidemiol Infect. 2010 Feb;138(2):183-91
references.pmid: 19925691