title: Estimate of the reproduction number of the 2015 Zika virus outbreak in Barranquilla, Colombia, and estimation of the relative role of sexual transmission.
abstract: In 2015, the Zika arbovirus (ZIKV) began circulating in the Americas, rapidly expanding its global geographic range in explosive outbreaks. Unusual among mosquito-borne diseases, ZIKV has been shown to also be sexually transmitted, although sustained autochthonous transmission due to sexual transmission alone has not been observed, indicating the reproduction number (R0) for sexual transmission alone is less than 1. Critical to the assessment of outbreak risk, estimation of the potential attack rates, and assessment of control measures, are estimates of the basic reproduction number, R0.
  
  
  
  We estimated the R0 of the 2015 ZIKV outbreak in Barranquilla, Colombia, through an analysis of the exponential rise in clinically identified ZIKV cases (n=359 to the end of November, 2015).
  
  
  
  The rate of exponential rise in cases was ρ=0.076days-1, with 95% CI [0.066,0.087] days-1. We used a vector-borne disease model with additional direct transmission to estimate the R0; assuming the R0 of sexual transmission alone is less than 1, we estimated the total R0=3.8 [2.4,5.6], and that the fraction of cases due to sexual transmission was 0.23 [0.01,0.47] with 95% confidence.
  
  
  
  This is among the first estimates of R0 for a ZIKV outbreak in the Americas, and also among the first quantifications of the relative impact of sexual transmission.
authors.affiliation: Arizona State University, Tempe, AZ, USA. Electronic address: smtowers@asu.edu.
authors.forename: Sherry
authors.initials: S
authors.lastname: Towers
authors.affiliation: University of British Columbia, Vancouver, BC, Canada.
authors.forename: Fred
authors.initials: F
authors.lastname: Brauer
authors.affiliation: Arizona State University, Tempe, AZ, USA.
authors.forename: Carlos
authors.initials: C
authors.lastname: Castillo-Chavez
authors.affiliation: Universidad del Norte, Barranquilla, Atlantico, Colombia.
authors.forename: Andrew K I
authors.initials: AKI
authors.lastname: Falconar
authors.affiliation: Arizona State University, Tempe, AZ, USA.
authors.forename: Anuj
authors.initials: A
authors.lastname: Mubayi
authors.affiliation: Universidad del Norte, Barranquilla, Atlantico, Colombia.
authors.forename: Claudia M E
authors.initials: CME
authors.lastname: Romero-Vivas
mesh_terms: D000818:Animals; D050936:Basic Reproduction Number; D003105:Colombia / Q000453:epidemiology; D004196:Disease Outbreaks; D006801:Humans; D000071244:Zika Virus; D000071243:Zika Virus Infection / Q000453:epidemiology* / Q000635:transmission
keywords: Arboviruses; Basic reproduction number; Mathematical model; Sexually transmitted infections; Zika virus