The effects of weather and climate change on dengue

Abstract

Background: There is much uncertainty about the future impact of climate change on vector-borne diseases. Such uncertainty reflects the difficulties in modelling the complex interactions between disease, climatic and socioeconomic determinants. We used a comprehensive panel dataset from Mexico covering 23 years of province-specific dengue reports across nine climatic regions to estimate the impact of weather on dengue, accounting for the effects of non-climatic factors.

Methods and findings: Using a Generalized Additive Model, we estimated statistically significant effects of weather and access to piped water on dengue. The effects of weather were highly nonlinear. Minimum temperature (Tmin) had almost no effect on dengue incidence below 5 °C, but Tmin values above 18 °C showed a rapidly increasing effect. Maximum temperature above 20 °C also showed an increasing effect on dengue incidence with a peak around 32 °C, after which the effect declined. There is also an increasing effect of precipitation as it rose to about 550 mm, beyond which such effect declines. Rising access to piped water was related to increasing dengue incidence. We used our model estimations to project the potential impact of climate change on dengue incidence under three emission scenarios by 2030, 2050, and 2080. An increase of up to 40% in dengue incidence by 2080 was estimated under climate change while holding the other driving factors constant.

Conclusions: Our results indicate that weather significantly influences dengue incidence in Mexico and that such relationships are highly nonlinear. These findings highlight the importance of using flexible model specifications when analysing weather-health interactions. Climate change may contribute to an increase in dengue incidence. Rising access to piped water may aggravate dengue incidence if it leads to increased domestic water storage. Climate change may therefore influence the success or failure of future efforts against dengue.

Figure 1. Time series of average monthly dengue incidence in Mexico (cases/100,000 people) over the period January 1985 to December 2007.

Figure 2. GAM-estimated relationships.

The figure shows the GAM estimated relationships between average monthly dengue incidence and (A) Tmin_1∶2, (B) Tmax_1∶2, (C) Precipitation_1∶2, and (D) the proportion of the population with access to piped water. Solid lines indicate the average expected number of dengue cases (cases/100,000 people per month); dashed lines indicate the estimated 95% Bayesian estimation confidence intervals.

Figure 3. Changes in annual dengue incidence under climate change.

The figure shows the GAM-estimated 1970–1999 average annual dengue incidence (cases/100,000 people) across Mexico for the baseline scenario (top), and the estimated difference in mean annual dengue incidence relative to that baseline (cases/100,000 people) by 2030, 2050, and 2080 under the A1B, A2, and B1 climate change scenarios.