title: Initial human transmission dynamics of the pandemic (H1N1) 2009 virus in North America.
abstract: BACKGROUND
  Between 5 and 25 April 2009, pandemic (H1N1) 2009 caused a substantial, severe outbreak in Mexico, and subsequently developed into the first global pandemic in 41 years. We determined the reproduction number of pandemic (H1N1) 2009 by analyzing the dynamics of the complete case series in Mexico City during this early period.
  
  
  METHODS
  We analyzed three mutually exclusive datasets from Mexico City Distrito Federal which constituted all suspect cases from 15 March to 25 April: confirmed pandemic (H1N1) 2009 infections, non-pandemic influenza A infections and patients who tested negative for influenza. We estimated the initial reproduction number from 497 suspect cases identified prior to 20 April, using a novel contact network methodology incorporating dates of symptom onset and hospitalization, variation in contact rates, extrinsic sociological factors, and uncertainties in underreporting and disease progression. We tested the robustness of this estimate using both the subset of laboratory-confirmed pandemic (H1N1) 2009 infections and an extended case series through 25 April, adjusted for suspected ascertainment bias.
  
  
  RESULTS
  The initial reproduction number (95% confidence interval range) for this novel virus is 1.51 (1.32-1.71) based on suspected cases and 1.43 (1.29-1.57) based on confirmed cases before 20 April. The longer time series (through 25 April) yielded a higher estimate of 2.04 (1.84-2.25), which reduced to 1.44 (1.38-1.51) after correction for ascertainment bias.
  
  
  CONCLUSIONS
  The estimated transmission characteristics of pandemic (H1N1) 2009 suggest that pharmaceutical and non-pharmaceutical mitigation measures may appreciably limit its spread prior the development of an effective vaccine.
authors.affiliation: Division of Mathematical Modeling, British Columbia Centre for Disease Control, Vancouver, British Columbia, Canada. babak.pourbohloul@bccdc.ca
authors.forename: Babak
authors.initials: B
authors.lastname: Pourbohloul
authors.forename: Armando
authors.initials: A
authors.lastname: Ahued
authors.forename: Bahman
authors.initials: B
authors.lastname: Davoudi
authors.forename: Rafael
authors.initials: R
authors.lastname: Meza
authors.forename: Lauren A
authors.initials: LA
authors.lastname: Meyers
authors.forename: Danuta M
authors.initials: DM
authors.lastname: Skowronski
authors.forename: Ignacio
authors.initials: I
authors.lastname: Villaseñor
authors.forename: Fernando
authors.initials: F
authors.lastname: Galván
authors.forename: Patricia
authors.initials: P
authors.lastname: Cravioto
authors.forename: David J D
authors.initials: DJ
authors.lastname: Earn
authors.forename: Jonathan
authors.initials: J
authors.lastname: Dushoff
authors.forename: David
authors.initials: D
authors.lastname: Fisman
authors.forename: W John
authors.initials: WJ
authors.lastname: Edmunds
authors.forename: Nathaniel
authors.initials: N
authors.lastname: Hupert
authors.forename: Samuel V
authors.initials: SV
authors.lastname: Scarpino
authors.forename: Jesús
authors.initials: J
authors.lastname: Trujillo
authors.forename: Miguel
authors.initials: M
authors.lastname: Lutzow
authors.forename: Jorge
authors.initials: J
authors.lastname: Morales
authors.forename: Ada
authors.initials: A
authors.lastname: Contreras
authors.forename: Carolina
authors.initials: C
authors.lastname: Chávez
authors.forename: David M
authors.initials: DM
authors.lastname: Patrick
authors.forename: Robert C
authors.initials: RC
authors.lastname: Brunham
mesh_terms: D016358:Contact Tracing; D004196:Disease Outbreaks; D004812:Epidemiologic Methods; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000472:pathogenicity*; D007251:Influenza, Human / Q000453:epidemiology / Q000503:physiopathology / Q000635:transmission* / Q000821:virology; D008800:Mexico / Q000453:epidemiology; D009656:North America / Q000453:epidemiology; D058873:Pandemics
references.citation: Emerg Infect Dis. 2006 Jan;12(1):9-14
references.pmid: 16494710
references.citation: Phys Rev E Stat Nonlin Soft Matter Phys. 2002 Jul;66(1 Pt 2):016128
references.pmid: 12241447
references.citation: MMWR Morb Mortal Wkly Rep. 2009 May 8;58(17):470-2
references.pmid: 19444151
references.citation: Science. 2009 Jun 19;324(5934):1557-61
references.pmid: 19433588
references.citation: Nature. 2004 Dec 16;432(7019):904-6
references.pmid: 15602562
references.citation: Science. 2005 Aug 12;309(5737):1083-7
references.pmid: 16079251
references.citation: Nature. 2005 Sep 8;437(7056):209-14
references.pmid: 16079797
references.citation: J Theor Biol. 2005 Jan 7;232(1):71-81
references.pmid: 15498594
references.citation: PLoS Med. 2006 Oct;3(10):e387
references.pmid: 17020406
references.citation: Salud Publica Mex. 2006 Sep-Oct;48(5):379-84
references.pmid: 17063821
references.citation: MMWR Morb Mortal Wkly Rep. 2009 May 8;58(17):467-70
references.pmid: 19444150
references.citation: J R Soc Interface. 2009 Dec 6;6(41):1121-34
references.pmid: 19324673
references.citation: Lancet. 2007 Jul 14;370(9582):109-110
references.pmid: 17630021
references.citation: Emerg Infect Dis. 2005 Aug;11(8):1249-56
references.pmid: 16102315
references.citation: J Theor Biol. 2003 Sep 7;224(1):1-8
references.pmid: 12900200
references.citation: J Theor Biol. 2006 Jun 7;240(3):400-18
references.pmid: 16300796
references.citation: Annu Rev Med. 2005;56:357-81
references.pmid: 15660517