Potential Changes in the Distribution of Dengue Transmission under Climate Warming

Abstract

The purpose of the present paper is to document an initial attempt to quantify the influence of warming temperatures on the intensity and distribution of dengue transmission throughout the world using an expression of vectorial capacity modified to reflect the role of temperature on development and survival of the vector and virus. We rearranged the traditional vectorial capacity expression (the mean number of potentially infective contacts made by a mosquito population per infectious person per unit time) to develop an equation for the critical density threshold, an estimate of the number of adult female vectors required to just maintain the virus in a susceptible human population. In this expression, temperature influences adult survival, the lengths of the gonotrophic cycle and the extrinsic incubation period of the virus in the vector, and vector size, a factor that indirectly influences the biting rate. Before making projections for warming scenarios of current climate plus 2 or 4 degrees C, we validate our technique by successfully comparing model projections and the observed spatial, temporal, and altitudinal distribution of dengue using current climate in five cities that are endemic or have had epidemics in the past. Our results indicate that the current warming projection of the International Council of Scientific Unions and the Intergovernmental Panel on Climate Change of 2 degrees C by the end of the next century can be expected to result in a potential increase in the latitudinal and altitudinal range of dengue; the potential duration of the transmission season will also increase in temperate locations as well. We discuss how an increase in temperature-related transmission intensity can be expected to lower the average ages of primary and secondary infections and thereby significantly increase the proportion of secondary infections occurring among infants and adolescents, the ages especially susceptible to dengue hemorrhagic fever and shock syndrome.

Climate change and mosquito-borne disease.

“…Much of the recent speculation on the possible effects of climate change on mosquito-borne disease has focused on rudimentary concepts of their transmission dynamics (30,(46)(47)(48). An example is vectorial capacity, a convenient way of expressing transmission risk:…”

Calculating the survival rate and estimated population density of gravid Aedes aegypti (Diptera, Culicidae) in Rio de Janeiro, Brazil

“…Since the probability that a mosquito acquires dengue is influenced by virus titer, we simulated vectorial capacity using three probability values for c: 0.30, 0.45 and 0.55, with virus titer ranging between 10 5 and 10 6 (MID 50 )/ml 25,26 . The duration of the extrinsic incubation period would be set at 10 days 23 .…”

Temporal analysis of the relationship between dengue and meteorological variables in the city of Rio de Janeiro, Brazil, 2001-2009

“…According to various studies, temperature has an impact on the population size, maturation period, blood-sucking activity, and survival rate of Ae. aegypti 14,15,16,17 . The relationship to precipitation depends on local characteristics and whether breeding sites are maintained predominantly by rain 3 .…”