title: [An epidemiological investigation on a food-born outbreak of noroviru caused by Sydney 2012 G II.4 strain].
abstract: OBJECTIVE
  To identify the source of infection, route of transmission and risk factors related to a cluster of acute gastroenteritis cases in a university of Guangzhou.
  
  
  METHODS
  Cases were identified according to the definition. Descriptive epidemiological approaches and case-control study designs were employed in the analysis. All the samples were tested for norovirus by RT-PCR. Positive samples were subjected to both nucleotide sequence and homology analysis.
  
  
  RESULTS
  A total of 141 cases related to norovirus gastroenteritis were identified in January 8 to 21, 2013, with the attack rate as 8.5 per thousand (141/16,600). The peak in morbidity was seen on January 8 to 9. No clustering was found in different classes or dormitories. Results from the case-control study revealed that early cases were infected in Restaurant A (OR = 3.46, 95% CI: 1.07-11.16) and the cold shredded chicken set meal (OR = 17.82, 95% CI: 4.46-78.17) served at lunch (OR = 4.34, 95% CI: 1.18 -17.37) on January 7 was under suspicion. A total of 266 samples, including rectal swabs from the patients and kitchen wokers, leftover food and environmental swabs, were collected. Twenty-one samples (collected from 17 persons) were positive for norovirus by RT-PCR. About 29.6% (8/27) of the kitchen workers in the Restaurant A were tested positive for the virus. The pathogen was identified as the new norovirus genotype II.4 variant, termed Sydney 2012. The virus strains isolated from the patients among student and staff and the kitchen workers were 100% identical in their nucleotide sequence.
  
  
  CONCLUSIONS
  This was the first reported acute gastroenteritis outbreak caused by the new norovirus genotype II.4 variant, Sydney 2012, which showed that the food was contaminated by the asymptomatic kitchen workers who carried the virus.
authors.affiliation: Guangzhou Center for Disease Control and Prevention, Guangzhou 510440, China.
authors.forename: Wen-Feng
authors.initials: WF
authors.lastname: Cai
authors.affiliation: Guangzhou Center for Disease Control and Prevention, Guangzhou 510440, China.
authors.forename: Hua-Ping
authors.initials: HP
authors.lastname: Xie
authors.affiliation: Guangzhou Center for Disease Control and Prevention, Guangzhou 510440, China.
authors.forename: Yu-Fei
authors.initials: YF
authors.lastname: Liu
authors.affiliation: Guangzhou Center for Disease Control and Prevention, Guangzhou 510440, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Yuan
authors.affiliation: Guangzhou Center for Disease Control and Prevention, Guangzhou 510440, China.
authors.forename: Xin-Cai
authors.initials: XC
authors.lastname: Xiao
authors.affiliation: Guangzhou Center for Disease Control and Prevention, Guangzhou 510440, China.
authors.forename: Peng
authors.initials: P
authors.lastname: Ding
authors.affiliation: Guangzhou Center for Disease Control and Prevention, Guangzhou 510440, China.
authors.forename: Chun
authors.initials: C
authors.lastname: Chen
authors.affiliation: Conghua Center for Disease Control and Prevention, Guangzhou.
authors.forename: Du
authors.initials: D
authors.lastname: Zhang
authors.affiliation: Guangzhou Center for Disease Control and Prevention, Guangzhou 510440, China.
authors.forename: Jian-Dong
authors.initials: JD
authors.lastname: Chen
authors.affiliation: Guangzhou Center for Disease Control and Prevention, Guangzhou 510440, China.
authors.forename: Xiao-Wei
authors.initials: XW
authors.lastname: Ma
authors.affiliation: Guangzhou Center for Disease Control and Prevention, Guangzhou 510440, China.
authors.forename: Jin-Mei
authors.initials: JM
authors.lastname: Geng
authors.affiliation: Panyu District Center for Disease Control and Prevention, Guangzhou.
authors.forename: Dong-Ming
authors.initials: DM
authors.lastname: Lin
authors.affiliation: Panyu District Center for Disease Control and Prevention, Guangzhou.
authors.forename: Gui-Xiong
authors.initials: GX
authors.lastname: Lian
authors.affiliation: Guangzhou Center for Disease Control and Prevention, Guangzhou 510440, China.
authors.forename: Zhi-Cong
authors.initials: ZC
authors.lastname: Yang
mesh_terms: D000293:Adolescent; D000328:Adult; D017250:Caliciviridae Infections / Q000453:epidemiology*; D016022:Case-Control Studies; D002681:China / Q000453:epidemiology; D004196:Disease Outbreaks; D005260:Female; D005517:Foodborne Diseases / Q000453:epidemiology* / Q000821:virology; D005759:Gastroenteritis / Q000453:epidemiology* / Q000821:virology; D006801:Humans; D008297:Male; D029322:Norovirus