Reemergence of Chikungunya Virus in Cambodia

Veasna Duong, Anne-Claire Andries, Chantha Ngan, Touch Sok, Beat Richner, Nima Asgari-Jirhandeh, Steve Bjorge, Rekol Huy, Sovann Ly, Denis Laurent, Bunheng Hok, Maria Concepcion Roces, Sivuth Ong, Meng Chuor Char, Vincent Deubel, Arnaud Tarantola, and Philippe Buchy

Author affiliations: Author affiliations: Institut Pasteur in Cambodia, Phnom Penh, Cambodia (V. Duong, A.-C. Andries, S. Ong, V. Deubel, A. Tarantola, P. Buchy); Ministry of Health, Phnom Penh (C. Ngan, T. Sok, R. Huy, S. Ly, M.C. Char,); Jayavarman VII Hospital, Siem Reap, Cambodia (B. Richner, D. Laurent); World Health Organization, Phnom Penh (N. Asgari-Jirhandeh, S. Bjorge, M.C. Roces); Preah Vihear Provincial Health Department, Preah Vihear, Cambodia (B. Hok)

Abstract

Chikungunya virus (CHIKV), probably Asian genotype, was first detected in Cambodia in 1961. Despite no evidence of acute or recent CHIKV infections since 2000, real-time reverse transcription PCR of serum collected in 2011 detected CHIKV, East Central South African genotype. Spatiotemporal patterns and phylogenetic clustering indicate that the virus probably originated in Thailand.

Chikungunya virus (CHIKV; family Togaviridae; genus Alphavirus) is an arthropod-borne virus transmitted to humans by Aedes spp. mosquitoes (1). It is an enveloped, positive-sense, single-stranded RNA virus with a genome of ≈11.8 kb (2). Three genotypes have been identified: Western African, East Central South African (ECSA), and Asian (3).
First identified in Tanzania in the mid-1950s, CHIKV circulated in the 1960s in sub-Saharan Africa and several Asian countries (4,5). Reemergence of CHIKV (ECSA genotype) was reported in Democratic Republic of Congo in 1999–2000 (6,7) and in Kenya in 2004 (4). This genotype emerged in Comoros followed by Réunion Island, the Seychelles, Mauritius, Mayotte, and India in 2005 (the Indian Ocean outbreak); in Sri Lanka and Malaysia in 2006; in Singapore and Thailand in 2008; and in China in 2010 (8).
In Cambodia, CHIKV was first detected in 1961, probably the Asian genotype that was circulating in the region at that time (9). Since 2000, all blood specimens collected by the National Dengue Control Program, Ministry of Health Cambodia, during hospital-based surveillance of dengue and investigation of suspected dengue cases have been screened for IgM against CHIKV, dengue virus (DENV), Japanese encephalitis virus (JEV), and other arboviruses. Despite this testing, no evidence of acute or recent CHIKV infections has been found. To confirm CHIKV infection in samples positive by serologic testing, we conducted real-time reverse transcription PCR (RT-PCR) and complete genome sequencing of the samples. In 2011, we detected CHIKV ECSA genotype in patients in Cambodia and analyzed the phylogenetic origin of the strains.