title: The risk of chikungunya fever in a dengue-endemic area.
abstract: BACKGROUND
  Chikungunya, an alphavirus of the Togaviridae family, causes a febrile disease transmitted to humans by the bite of infected Aedes mosquitoes. This infection is reaching endemic levels in many Southeast Asian countries. Symptoms include sudden onset of fever, chills, headache, nausea, vomiting, joint pain with or without swelling, low back pain, and rash. According to the World Health Organization, there are 2 billion people living in Aedes-infested areas. In addition, traveling to these areas is popular, making the potential risk of infections transmitted by the bite of infected Aedes mosquitoes very high.
  
  
  METHODS
  We proposed a mathematical model to estimate the risk of acquiring chikungunya fever in an Aedes-infested area by taking the prevalence of dengue fever into account. The basic reproduction number for chikungunya fever R(0chik) can be written as a function of the basic reproduction number of dengue R(0dengue) by calculating the ratio R(0chik)/R(0dengue). From R(0chik), we estimated the force of infection and the risk of acquiring the disease both for local residents of a dengue-endemic area and for travelers to this area.
  
  
  RESULTS
  We calculated that R(0chik) is 64.4% that of R(0dengue). The model was applied to a hypothetical situation, namely, estimating the individual risk of acquiring chikungunya fever in a dengue-endemic area, both for local inhabitants (22% in steady state) and for visiting travelers (from 0.31% to 1.23% depending on the time spent in the area).
  
  
  CONCLUSIONS
  The method proposed based on the output of a dynamical model is innovative and provided an estimation of the risk of infection, both for local inhabitants and for visiting travelers.
authors.affiliation: School of Medicine, University of São Paulo, LIM 01-HCFMUSP, São Paulo, Brazil. edmassad@usp.br
authors.forename: Eduardo
authors.initials: E
authors.lastname: Massad
authors.forename: Stefan
authors.initials: S
authors.lastname: Ma
authors.forename: Marcelo Nascimento
authors.initials: MN
authors.lastname: Burattini
authors.forename: Ye
authors.initials: Y
authors.lastname: Tun
authors.forename: Francisco Antonio Bezerra
authors.initials: FA
authors.lastname: Coutinho
authors.forename: Li Wei
authors.initials: LW
authors.lastname: Ang
mesh_terms: D000330:Aedes; D018354:Alphavirus Infections / Q000453:epidemiology* / Q000635:transmission; D000818:Animals; D001210:Asia, Southeastern / Q000453:epidemiology; D002646:Chikungunya virus; D015897:Comorbidity; D003715:Dengue / Q000453:epidemiology* / Q000635:transmission; D019353:Endemic Diseases / Q000706:statistics & numerical data*; D006801:Humans; D007303:Insect Vectors; D015233:Models, Statistical; D015995:Prevalence; D018570:Risk Assessment; D012307:Risk Factors; D014195:Travel