Mobility and non-household environments: understanding dengue transmission patterns in urban contexts
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Households (HH) have been traditionally described as the main environments where people are at risk of dengue and other arbovirus infections. Mounting entomological evidence suggests a larger role for environments other than HH. Recently, an agent-based model (ABM) estimated that over half of infections occur in non-household (NH) environments such as workplaces, markets, and recreational sites. Despite the inferred importance of NH sites, we do not yet know how their urban spatial configurations, and human and vector mobility between them, affects their role in dengue transmission. To address this gap, we expanded an ABM calibrated with field data from Kenya to examine movement of people and vectors under different spatial configurations of buildings. We assessed the number of people traveling between HH and NH and the distances traveled, in three urban configurations: NH distributed randomly (scattered), concentrated in a single center, or clustered in multiple centers. Across simulations, the number of people moving was the most influential variable, with higher movement between HH and NH increasing case numbers. The number of cases was also higher when NH were scattered compared to centered or clustered. Intriguingly, the distance people traveled from HH to NH had little effect on dengue burden but influenced the spatial clustering of infections. These findings underscore the role of NH as major spreaders of infections between HH and NH environments, and the importance of human movement in driving dengue dynamics.
Author summary
Recent evidence describes a major role of non-household (NH) environments in dengue transmission. This new knowledge implies that spatial distribution of these locations and the movement of humans among them has implications in dynamics of transmission. However, these haven’t been evaluated neither together nor considering a differential role in transmission of urban environments. We modified a previously informed agent-based model to include spatial variables by assessing three different urban conformations, i.e. when NH are randomly distributed (scattered), centered, or grouped in differed clusters (clustered). On these, we also evaluated the movement of people from households (HH) to NH (both distance and number of individuals). Our findings, which includes a higher burden of dengue when NH are scattered and at higher levels of human movement, are aligned with the idea that infections are mainly happening in NH mediated by human mobilization. Infected people reach the households where local subpopulation of vector spread the virus to remaining inhabitants. This work highlights the role of NH and human mobility in dengue transmission.
