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Since 2000, the Government of Viet Nam has committed to provide rural communities with increased access to safe water through a variety of household water supply schemes (wells, ferrocement tanks and jars) and piped water schemes. One possible, unintended consequence of these schemes is the concomitant increase in water containers that may serve as habitats for dengue mosquito immatures, principally Aedes aegypti. To assess these possible impacts we undertook detailed household surveys of Ae. aegypti immatures, water storage containers and various socioeconomic factors in three rural communes in southern Viet Nam. Positive relationships between the numbers of household water storage containers and the prevalence and abundance of Ae. aegypti immatures were found. Overall, water storage containers accounted for 92-97% and 93-96% of the standing crops of III/IV instars and pupae, respectively. Interestingly, households with higher socioeconomic levels had significantly higher numbers of water storage containers and therefore greater risk of Ae. aegypti infestation. Even after provision of piped water to houses, householders continued to store water in containers and there was no observed decrease in water storage container abundance in these houses, compared to those that relied entirely on stored water. These findings highlight the householders' concerns about the limited availability of water and their strong behavoural patterns associated with storage of water. We conclude that household water storage container availability is a major risk factor for infestation with Ae. aegypti immatures, and that recent investment in rural water supply infrastructure are unlikely to mitigate this risk, at least in the short term.

Community-based perceptions and behaviour around water source preference, household water storage patterns and water use, and householders' knowledge and behaviour with respect to dengue etiology and transmission, were examined in three communes located in the Mekong Delta area in southern Vietnam. Through focus group discussions, most participants identified poorly screened or uncovered water containers (including household water storage containers and other types of artificial containers) as habitats for mosquitoes that transmit dengue viruses, and thereby demonstrated a clear understanding of the links between household water storage practices and the threat of dengue. Our qualitative analyses also revealed broader community-based concerns about the limited availability of water and strong preferences for storage of rainwater based upon perceptions of cost, quality and security of supply. These perceptions are central to shaping householders' responses to water infrastructure projects. The limited availability of water during the dry season and insufficient numbers of water storage containers are over-riding community concerns which provide an important context to understanding community behaviours and responses to public health interventions against dengue. Such concerns are important precursors to selecting the type of intervention.