A model for a chikungunya outbreak in a rural Cambodian setting: implications for disease control in uninfected areas

PLoS Negl Trop Dis. 2014 Sep 11;8(9):e3120. doi: 10.1371/journal.pntd.0003120. eCollection 2014 Sep.


Following almost 30 years of relative silence, chikungunya fever reemerged in Kenya in 2004. It subsequently spread to the islands of the Indian Ocean, reaching Southeast Asia in 2006. The virus was first detected in Cambodia in 2011 and a large outbreak occurred in the village of Trapeang Roka Kampong Speu Province in March 2012, in which 44% of the villagers had a recent infection biologically confirmed. The epidemic curve was constructed from the number of biologically-confirmed CHIKV cases per day determined from the date of fever onset, which was self-reported during a data collection campaign conducted in the village after the outbreak. All individuals participating in the campaign had infections confirmed by laboratory analysis, allowing for the identification of asymptomatic cases and those with an unreported date of fever onset. We develop a stochastic model explicitly including such cases, all of whom do not appear on the epidemic curve. We estimate the basic reproduction number of the outbreak to be 6.46 (95% C.I. [6.24, 6.78]). We show that this estimate is particularly sensitive to changes in the biting rate and mosquito longevity. Our model also indicates that the infection was more widespread within the population on the reported epidemic start date. We show that the exclusion of asymptomatic cases and cases with undocumented onset dates can lead to an underestimation of the reproduction number which, in turn, could negatively impact control strategies implemented by public health authorities. We highlight the need for properly documenting newly emerging pathogens in immunologically naive populations and the importance of identifying the route of disease introduction.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cambodia
  • Chikungunya Fever / epidemiology*
  • Chikungunya virus / isolation & purification
  • Communicable Disease Control / methods
  • Culicidae / virology
  • Disease Outbreaks*
  • Fever / epidemiology
  • Humans
  • Models, Biological*
  • Public Health
  • Stochastic Processes

Grant support

Work undertaken in Cambodia was directly funded by the Institut Pasteur du Cambodge, Monivong Boulevard, 12201 Phnom Penh, Cambodia. The European researchers were funded under the EU project DENFREE (http://www.denfree.eu/); Dengue Research Framework for Resisting Epidemics in Europe (grant agreement: 282 378), funded by the European Commission's Seventh Framework Research Programme. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.