title: A model for a chikungunya outbreak in a rural Cambodian setting: implications for disease control in uninfected areas.
abstract: 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.
authors.affiliation: Institut Català de Ciències del Clima, Barcelona, Spain.
authors.forename: Marguerite
authors.initials: M
authors.lastname: Robinson
authors.affiliation: Institut Pasteur du Cambodge, Phnom Penh, Cambodia.
authors.forename: Anne
authors.initials: A
authors.lastname: Conan
authors.affiliation: Institut Pasteur du Cambodge, Phnom Penh, Cambodia.
authors.forename: Veasna
authors.initials: V
authors.lastname: Duong
authors.affiliation: Institut Pasteur du Cambodge, Phnom Penh, Cambodia.
authors.forename: Sowath
authors.initials: S
authors.lastname: Ly
authors.affiliation: National Dengue Control Program, Ministry of Health, Phnom Penh, Cambodia.
authors.forename: Chantha
authors.initials: C
authors.lastname: Ngan
authors.affiliation: Institut Pasteur du Cambodge, Phnom Penh, Cambodia.
authors.forename: Philippe
authors.initials: P
authors.lastname: Buchy
authors.affiliation: Institut Pasteur du Cambodge, Phnom Penh, Cambodia.
authors.forename: Arnaud
authors.initials: A
authors.lastname: Tarantola
authors.affiliation: Institut Català de Ciències del Clima, Barcelona, Spain; Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Spain.
authors.forename: Xavier
authors.initials: X
authors.lastname: Rodó
mesh_terms: D000818:Animals; D002160:Cambodia; D065632:Chikungunya Fever / Q000453:epidemiology*; D002646:Chikungunya virus / Q000302:isolation & purification; D003140:Communicable Disease Control / Q000379:methods; D009033:Culicidae / Q000821:virology; D004196:Disease Outbreaks; D005334:Fever / Q000453:epidemiology; D006801:Humans; D008954:Models, Biological; D011634:Public Health; D013269:Stochastic Processes