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Nipah virus has caused recurring outbreaks in central and northwest Bangladesh (the “Nipah Belt”). Little is known about roosting behavior of the fruit bat reservoir, Pteropus giganteus, or factors driving spillover. We compared human population density and ecological characteristics of case villages and control villages (no reported outbreaks) to understand their role in P. giganteus roosting ecology and Nipah virus spillover risk. Nipah Belt villages have a higher human population density (P < 0.0001), and forests that are more fragmented than elsewhere in Bangladesh (0.50 versus 0.32 patches/km2, P < 0.0001). The number of roosts in a village correlates with forest fragmentation (r = 0.22, P = 0.03). Villages with a roost containing Polyalthia longifolia or Bombax ceiba trees were more likely case villages (odds ratio [OR] = 10.8, 95% confidence interval [CI] = 1.3–90.6). This study suggests that, in addition to human population density, composition and structure of the landscape shared by P. giganteus and humans may influence the geographic distribution of Nipah virus spillovers.

We respond to Valle and Clark,1 who assert that “conservation efforts may increase malaria burden in the Brazilian Amazon,” because the relationship between forest cover and malaria incidence was stronger than the effect of the deforestation rate.1 We contend that their conclusion is flawed because of limitations in their methodology that we discuss in detail. Most important are the exclusion of one-half the original data without a discussion of selection bias, the lack of model adjustment for either population growth or migration, and the crude classifications of land cover and protected areas that lead to aggregation bias.1 Of greater significance, we stress the need for caution in the interpretation of data that could have profound effects on regional land use decisions.