title: An internet-based epidemiological investigation of the outbreak of H7N9 Avian influenza A in China since early 2013.
abstract: BACKGROUND
  In early 2013, a new type of avian influenza, H7N9, emerged in China. It quickly became an issue of great public concern and a widely discussed topic on the Internet. A considerable volume of relevant information was made publicly available on the Internet through various sources.
  
  
  OBJECTIVE
  This study aimed to describe the outbreak of H7N9 in China based on data openly available on the Internet and to validate our investigation by comparing our findings with a well-conducted conventional field epidemiologic study.
  
  
  METHODS
  We searched publicly accessible Internet data on the H7N9 outbreak primarily from government and major mass media websites in China up to February 10, 2014. Two researchers independently extracted, compared, and confirmed the information of each confirmed H7N9 case using a self-designed data extraction form. We summarized the epidemiological and clinical characteristics of confirmed H7N9 cases and compared them with those from the field study.
  
  
  RESULTS
  According to our data updated until February 10, 2014, 334 confirmed H7N9 cases were identified. The median age was 58 years and 67.0% (219/327) were males. Cases were reported in 15 regions in China. Five family clusters were found. Of the 16.8% (56/334) of the cases with relevant data, 69.6% (39/56) reported a history of exposure to animals. Of the 1751 persons with a close contact with a confirmed case, 0.6% (11/1751) of them developed respiratory symptoms during the 7-day surveillance period. In the 97.9% (327/334) of the cases with relevant data, 21.7% (71/327) died, 20.8% (68/327) were discharged from a hospital, and 57.5% (188/327) were of uncertain status. We compared our findings before February 10, 2014 and those before December 1, 2013 with those from the conventional field study, which had the latter cutoff date of ours in data collection. Our study showed most epidemiological and clinical characteristics were similar to those in the field study, except for case fatality (71/327, 21.7% for our data before February 10; 45/138, 32.6% for our data before December 1; 47/139, 33.8% for the field study), time from illness onset to first medical care (4 days, 3 days, and 1 day), and time from illness onset to death (16.5 days, 17 days, and 21 days).
  
  
  CONCLUSIONS
  Findings from our Internet-based investigation were similar to those from the conventional field study in most epidemiological and clinical aspects of the outbreak. Importantly, publicly available Internet data are open to any interested researchers and can thus greatly facilitate the investigation and control of such outbreaks. With improved efforts for Internet data provision, Internet-based investigation has a great potential to become a quick, economical, novel approach to investigating sudden issues of great public concern that involve a relatively small number of cases like this H7N9 outbreak.
authors.affiliation: School of Public Health and Primary Care, The Chinese University of Hong Kong, Hong Kong, Hong Kong, China (Hong Kong).
authors.forename: Chen
authors.identifier: http://orcid.org/0000-0001-7471-1516
authors.initials: C
authors.lastname: Mao
authors.forename: Xin-Yin
authors.identifier: http://orcid.org/0000-0003-3772-2376
authors.initials: XY
authors.lastname: Wu
authors.forename: Xiao-Hong
authors.identifier: http://orcid.org/0000-0003-3594-2367
authors.initials: XH
authors.lastname: Fu
authors.forename: Meng-Yang
authors.identifier: http://orcid.org/0000-0002-1825-0097
authors.initials: MY
authors.lastname: Di
authors.forename: Yuan-Yuan
authors.initials: YY
authors.lastname: Yu
authors.forename: Jin-Qiu
authors.identifier: http://orcid.org/0000-0003-0016-776X
authors.initials: JQ
authors.lastname: Yuan
authors.forename: Zu-Yao
authors.identifier: http://orcid.org/0000-0003-2386-2431
authors.initials: ZY
authors.lastname: Yang
authors.forename: Jin-Ling
authors.identifier: http://orcid.org/0000-0003-0536-0083
authors.initials: JL
authors.lastname: Tang
mesh_terms: D000328:Adult; D002648:Child; D002681:China / Q000453:epidemiology; D004196:Disease Outbreaks; D004812:Epidemiologic Methods; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D007223:Infant; D064766:Influenza A Virus, H7N9 Subtype; D007251:Influenza, Human / Q000453:epidemiology*; D020407:Internet; D008297:Male; D008875:Middle Aged
keywords: Internet; big data; disease outbreaks; epidemiology; influenza A virus, H7N9 subtype