FIGURE 1. Correlation between simulated, climate-driven variations in Aedes aegypti mosquito density and observed variations in dengue and DHF cases.

Using a computer model of mosquito physiology and development, estimated changes in the relative abundance of Aedes aegypti that were driven only by month-to-month and year-to-year variations in temperature, humidity, solar radiation and rainfall were analysed. The simulated, climate-induced variations in mosquito density were then compared to reported cases of dengue and DHF across many nations of the world that covered at least one degree of latitude and longitude and had at least five years of dengue caseload data. In many countries of Central America and Southeast Asia, the relationship is statistically significant (P < 0.05). For example, climate-driven fluctuations in Ae. aegypti densities appear to be related to annual variations in dengue/DHF cases in Honduras, Nicaragua and Thailand as shown. These represent relatively small-area countries; for larger countries endemic for dengue such as Brazil, China, India and Mexico, the association is not significant, as might be expected because the disease data was at the country level. Graphs adapted from ref. 32.