Forest Cover and Dengue in Costa Rica: Panel Data Analysis of the Effects of Forest Cover Change on Hospital Admissions and Outbreaks

Abstract

Approximately 3.9 billion people are at risk of infection with dengue fever, a group of viruses transmitted by mosquitoes (Halstead in Annu Rev Entomol 53:273–291, 2008. https://doi.org/10.1146/annurev.ento.53.103106.0933262008; WHO in WHO | Dengue and severe dengue, Geneva, 2018). In 2019, Central America suffered a severe dengue epidemic (Salinas Maldonado in Un brote de dengue pone en alerta a Centroamérica | Sociedad | EL PAÍS, El País, 2019). Costa Rica witnessed an almost doubling of the number of dengue cases in the first 24 epidemiological weeks of 2019 compared to the same period in the previous year (Ávalos in Costa Rica casi duplica número de enfermos de dengue en lo que va del año, con respecto al 2018, La Nación, 2019). In the Americas, forest cover is thought to diminish anthropogenic habitats for mosquitoes while also increasing the presence of their predators (Vasilakis et al. in Nat Rev Microbiol 9:532–541, 2011. https://doi.org/10.1038/nrmicro2595; Weterings et al. in Basic Appl Ecol 15:486–495, 2014a. https://doi.org/10.1016/J.BAAE.2014.07.006). In this study, we estimate the marginal effects of increasing forest cover on dengue prevalence in Costa Rica using econometric models to relate hospital admission records to forest cover maps from 2001 and 2011. We find that increasing the percentage of forest cover significantly decreases both the number of hospital admissions for dengue and the probability of an outbreak. Using the same models, we predict that if forest cover had been increased by three percentage points during 10 years (0.29% per year), 29 dengue hospital admissions per year might have been avoided (around 1.4% of cases in the country, depending on the year). This represents average savings between USD 7230 and 82,207 per year, depending on the severity of the impact on individuals with dengue. Our study demonstrates that forest conservation can serve as a public health investment, enhancing social welfare by mitigating illness and reducing associated healthcare expenditures. Our results must be interpreted with caution, however, as the characteristics of our data prevent us from confirming that the estimated negative effect of forest cover on dengue represents a causal impact.