Long-Lasting Immune Protection and Other Epidemiological Findings after Chikungunya Emergence in a Cambodian Rural Community, April 2012.

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.

Seroprevalence of anti-H5 antibody in rural Cambodia, 2007.

BACKGROUND: Since 2005, eight patients with H5N1 infection were laboratory confirmed in Cambodia. Despite the widespread of highly pathogenic avian influenza H5N1 virus and the intense exposure to poultry, there is growing evidence that H5N1 viruses may not be easily transmitted to human. OBJECTIVES: To evaluate the frequency of H5N1 transmission in rural Cambodia, to identify potential risk factors for H5N1 in humans and to explore the extent of asymptomatic and clinically mild illness among humans. STUDY DESIGN: A seroepidemiologic survey was conducted, 9 weeks after the recognition that H5N1 infection caused the death of a 13 years old female in April 2007. Blood specimens were collected from 700 participants for H5N1 serological testing. All participants were interviewed with standardized questionnaire to collect information about poultry exposure. RESULTS: Eighteen (2.6%) of the 700 villagers were tested positive cases for H5N1 antibodies. These 18 individuals were more likely than seronegative participants to report bathing or swimming in the community pond (p=0.04). CONCLUSIONS: The seroprevalence of H5N1 antibodies was higher than previously reported in the other investigations conducted in Cambodia and Thailand. This finding reinforces the overwhelming evidence that the virus continues to circulate widely in settings where human have high exposure to poultry. Our results, provides additional evidence suggesting that bathing or swimming in the community ponds, remains important potential risk factor for H5N1 infection. Both wild birds and domestic poultry have free access to these ponds which are also used for aquaculture through the dumping of poultry feces for fish feeding.