Of special concern lately has been the effect of global warming on the incidence and spread of dengue disease. Although there are probably no effects on DENV replication in humans, if environmental temperatures rise, many investigators presume there might be an effect on virus transmission by mosquitoes. This is derived from the fact that increases in temperature (along with increases in rainfall) directly affect mosquito development (from larval to adult stages) and their populations can increase dramatically. Also, increases in average temperatures in new climes might make conditions favorable for mosquito breeding and the establishment of new populations. This could surely lead to more chances of exposure to mosquito bites for the human population and thus for infection by mosquito-borne viruses. However, the reason why many mosquito-borne diseases have yet to affect large populations in developed nations seems to be a lack of exposure to mosquito bites; air-conditioning and human behavior have been shown to reduce DENV transmission in the southern United States (Reiter et al. 2003) . That is, human activities and their impact on local ecology have generally been more significant in increasing dengue prevalence; thus, dengue disease seems to be influenced more by economic than climatic factors (Gubler et al. 2001; Reiter 2001 ). Also, research described below has shown that increases in temperature might have more of an impact on selecting for those virulent genotypes that are already being transmitted by mosquitoes. Mosquito survival rates and the time it takes for a virus to infect and be transmitted by the mosquito seem to be more important in this context.