Malaria and Dengue

According to the World Health Organization Malaria is the most deadly vector borne disease, killing more than 1.2 million people per year. They also report that Dengue fever and its associated disease, Dengue Hemorrhagic Fever, is the fastest growing vector borne disease. Both Malaria and Dengue are arboviruses (carried by mosquito vectors). However, Dengue is spread by the Aedes mosquito whereas Malaria is spread by the Anopheles mosquito. Most mosquito species have limited geographical regions. Thus, the different species of mosquitoes determine the region where the different diseases occur. Both the Aedes and Anopheles mosquitoes are predominately found in the tropics and thus as climate continues to change their expanding geographic distributions will be similar.

Malaria is most prevalent and transmissible in regions with warm and humid environments. As such, predicting the future range of the mosquito vector focuses on areas with increasing temperatures and adequate annual precipitation. Similarly, Dengue thrives in the tropics. 

The vast majority of disease predicting models focused on climate change have to simplify the contributing factors and tend to limit input and interactions as depicted in the flow chart (below).

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Since the mosquito species that carries the malaria causing pathogen typically does not inhabit geographic areas with cooler climates, the disease is uncommon in such areas. For example, a study focusing on malaria prevalence and distribution in East Africa highlands found there to be a strong link between increasing temperatures and wetland areas in these regions and the recent increase in malaria incidence rate. 

From a human health perspective, such a change in disease range is of particular concern when the disease spreads to areas where the human population has not been previously exposed; a large non-immune, susceptible population experiences high illness and death rates. A recent study focusing on highlands, also suggested that a change of about 2°C could put uninfected regions neighboring Malaria infected regions at risk of experiencing an epidemic. 

Similarly, Dengue transmission depends on mosquitoes and is thus also found in regions with the optimal tropical climate.  As with Malaria, research has found that with increased rainfall and temperatures Dengue is spreading into new regions with these optimal conditions. Dengue is being seen at a much higher rate in the Americas. 


The Pan American Health Organization reports that “the number of cases reported in the Americas increased from 66,000 in 1980 to 552,000 in 2006”. Mexico also has recently been experiencing an epidemic of Dengue. According to Mexico's National Center for Epidemiology and Disease Control, since 2001 there has been an increase in Dengue cases by more than 600 percent. 


The following graphs support the general trend of these findings (at right).