Characterizing dengue transmission in rural areas: A systematic review

Abstract

Dengue has historically been considered an urban disease associated with dense human populations and the built environment. Recently, studies suggest increasing dengue virus (DENV) transmission in rural populations. It is unclear whether these reports reflect recent spread into rural areas or ongoing transmission that was previously unnoticed, and what mechanisms are driving this rural transmission. We conducted a systematic review to synthesize research on dengue in rural areas and apply this knowledge to summarize aspects of rurality used in current epidemiological studies of DENV transmission given changing and mixed environments. We described how authors defined rurality and how they defined mechanisms for rural dengue transmission. We systematically searched PubMed, Web of Science, and Embase for articles evaluating dengue prevalence or cumulative incidence in rural areas. A total of 106 articles published between 1958 and 2021 met our inclusion criteria. Overall, 56% (n = 22) of the 48 estimates that compared urban and rural settings reported rural dengue incidence as being as high or higher than in urban locations. In some rural areas, the force of infection appears to be increasing over time, as measured by increasing seroprevalence in children and thus likely decreasing age of first infection, suggesting that rural dengue transmission may be a relatively recent phenomenon. Authors characterized rural locations by many different factors, including population density and size, environmental and land use characteristics, and by comparing their context to urban areas. Hypothesized mechanisms for rural dengue transmission included travel, population size, urban infrastructure, vector and environmental factors, among other mechanisms. Strengthening our understanding of the relationship between rurality and dengue will require a more nuanced definition of rurality from the perspective of DENV transmission. Future studies should focus on characterizing details of study locations based on their environmental features, exposure histories, and movement dynamics to identify characteristics that may influence dengue transmission.

Fig 1. PRISMA diagram of articles included in our analysis where “n” represents the number of articles and “a” represents the number of estimates.

From: Moher D, Liberati A, Tetzlaff J, Altman DG, The PRISMA Group (2009). Preferred Reporting Items for Systematic Reviews and Meta-Analyses: The PRISMA Statement. PLoS Med 6(7): e1000097. doi:10.1371/journal.pmed1000097.

Fig 2. Map of study locations.

The size of dot corresponds to the number of estimates. The basemap is publicly available at https://www.naturalearthdata.com/downloads/50m-raster-data/50m-bathymetry/.

Fig 3. Distribution of rural to urban dengue incidence and prevalence ratios.

Each dot represents the average incidence or prevalence ratio grouped by direction of the estimate. The size and number of each dot represents the number of estimates. Red-colored estimates signify that incidence/prevalence was higher in urban areas; green-colored estimates signify that incidence/prevalence was equal between rural and urban areas (i.e., had confidence intervals that crossed the null value); and blue-colored estimates signify that incidence/prevalence was higher in rural areas.