5 Monivong Boulevard, P.O Box. 983, Phnom Penh, Cambodia [email protected]

The East-Central South African strain of Chikungunya is emerging in Asia since 2006, first in the Indian Subcontinent then Thailand.  It was identified in Cambodia in 2011 and caused epidemics in 2012. Little is known of the transmission dynamics of this Chikungunya re-emergence in an Asian setting, or of its medium- and long-term consequences in an Asian population.

Financial support

The outbreak investigation and serosurvey was supported by the World Health Organization.

Outbreak investigation and report

[email protected] team leaders

Tarantola A. ; Ly S.

Objective

Provide data to guide health planning efforts and prioritization of resources for Chikungunya control, both in Cambodia and nearby, hereto unaffected countries such as Vietnam and Laos.

Core of the project

IPC conducted the first full documentation of a re-emergent Chikungunya outbreak in Asia. The R0 is  being computed for the first time since the epidemic. In La Réunion

The report describes the dynamics and characteristics of a Chikungunya epidemic in a typical Cambodian village, including attack rates, end-of-epidemic seroprevalence and asymptomatic rates. In all, 425 persons in 98 homes were visited a village with a population of 695 in 134 homes where an outbreak had been described. The outbreak had lasted about 6 weeks. Families had been affected throughout the village, with a symptomatic attack rate estimated at 66.6% of the population (joint pains, and/or fever, and/or rash). In one family visited, one middle-aged mother of two died of a febrile neurological syndrome two hours after admission to the provincial hospital. Screening was undertaken at IPC’s virology unit to detect Chikungunya-specific IgM antibodies in dry blood spots. Testing found 188 CHIKV-IgM seropositives for a serological attack rate estimated at 44.2%, including 5.3% asymptomatic infections, for a total of 190 (44.7%) CHIKV-infected cases with the 2 additional cases positive in PCR. Prevalence was around 50% of the population up to the age of 50, age beyond which the attack rate fell, probably due to higher population immunity in these persons, possibly due to exposure in the early 1960s. The children of the suspect fatal case both showed serological signs of recent CHIKV infection. Two febrile cases were found viremic for CHIKV.

Publication

Centers for Disease Control and Prevention (CDC). Chikungunya outbreak – Cambodia, February-March 2012.MMWR Morb Mortal Wkly Rep. 2012 Sep 21; 61:737-40.

R0

[email protected] team leaders

Conan A., Tarantola A.  w/ M. Robinson and  J. Ródó, IC3, Barcelona

Objective:

To document the R0 of the outbreak described in Trapeang Roka village in Spring 2012

Core of the project

Data was provided for a Chikungunya outbreak in Cambodia. The data spanned a period of 48 days between 07/02/2012 and 25/03/2012 inclusive and consisted of 188 laboratory confirmed cases of Chikungunya. Each confirmed case was indexed by the outbreak day on which it occurred, where t = 0 indicates the start date of the epidemic on February 7th. The cumulative number of cases on day t was denoted by Zt, where t 2 [0; 47]. To estimate the value of the reproduction number R0, the data provided was fitted to a deterministic SEIR model for a Chikungunya outbreak in Reunion Island (Dumont et al, 2008). The model is being finalized and data should be available for the first publication of an outbreak R0 of Chikungunya outside La Réunion Island.