Abstract
The East/Central/South African genotype of Chikungunya virus with the E1-A226V mutation emerged in 2011 in Cambodia and spread in 2012. An outbreak of 190 cases was documented in Trapeang Roka, a rural village. We surveyed 425 village residents within 3–4 weeks after the outbreak, and determined the sensitivity and specificity of case definitions and factors associated with infection by CHIKV. Self-reported clinical presentation consisted mostly of fever, rash and arthralgia. The presence of all three clinical signs or symptoms was identified as the most sensitive (67%) and specific (84%) self-reported diagnostic clinical indicator compared to biological confirmation by MAC-ELISA or RT-PCR used as a reference. Having an indoor occupation was associated with lower odds of infection compared with people who remained at home (adjOR 0.32, 95%CI 0.12–0.82). In contrast with findings from outbreaks in other settings, persons aged above 40 years were less at risk of CHIKV infection, likely reflecting immune protection acquired when Chikungunya circulated in Cambodia before the Khmer Rouge regime in 1975. In view of the very particular history of Cambodia, our epidemiological data from Trapeang Roka are the first to support the persistence of CHIKV antibodies over a period of 40 years.
Highlights
Chikugunya is caused by an alphavirus transmitted by the bite of Aedes mosquitoes
Few data are available on the risk factors associated with infection by the East/Central/South African (ECSA) chikungunya virus (CHIKV) strain, and most previous studies have been conducted in endemic settings or during emergence of the virus
The findings that will guide surveillance, risk assessment and public health prevention and response should originate mainly from careful epidemiological documentation in the community of the true health burden of disease, risk factors associated with infection and the performance of clinical case definitions
Summary
Chikugunya is caused by an alphavirus transmitted by the bite of Aedes mosquitoes In humans, it is mostly a self-limiting illness marked with debilitating joint pains but severe illness occurs in about 1 clinical case in 1000 [1]. In 2005, a major epidemic in La Réunion island [6] displayed different epidemiological characteristics than previous outbreaks, with a higher attack rate and causing a number of deaths Genetic analysis attributed this outbreak to a mutated strain of the East/Central/South African (ECSA) strain of CHIKV bearing the E1-A226V and other mutations on the E2 glycoprotein gene [7,8], termed the Indian Ocean Lineage (IOL) strain [8]. Chikungunya poses a real and imminent threat to all yet unaffected areas where Aedes aegypti or Aedes albopictus are present, including various regions of Europe [28], the USA [29], Brazil [30] or Australia [31]
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