Malaria and Climate Change
The maps and data on this page are based on a study called "Mapping Physiological Suitability Limits for Malaria in Africa Under Climate Change" by Ryan et al. 2015.
Ryan and her team created models of current and future Malaria transmission in Africa, based on the Anopheles mosquito's ability to transmit disease. Some of the variables that the researchers included in their model were the mosquito's optimal temperature range, the climate of the region, moisture availability and population density.
The researchers found that the changing climate will increase the total area at risk for malaria transmission in some parts of Africa, while decreasing the strength of transmission for others. In the following sections we will walk through some of these findings and visualize them through maps.
Ryan et al. 2015
What is Malaria?
Click through the slides to learn more about Malaria Disease.
Symptoms and Spread
Malaria is a life-threatening disease with symptoms including high fevers, shaking chills, and flu-like fatigue. Malaria was eradicated from the United States in the 1950s, but is still present in parts of Africa, Asia and South America.
According to the 2020 World Malaria Report published by the World Health Organization, there were 229 million cases of malaria in 2019 and 409,000 deaths. Moreover, 94% of malaria cases and deaths in 2019 occurred in Africa.
Finding #1: Increase Area, Decrease Suitability
Researchers found that in future climate models, there will be a moderate increase in the overall land suitable for Malaria transmission at least one month out of the year in Africa. However, there will be a slight decrease in land that is most suitable for transmission to occur. In other words, more areas could experience malaria transmission, but the transmission season may not be for as long or as severe as it is currently.
The graph on the right shows this change in the area of land suitable for Malaria Transmission vs how strong the transmission potential is.
As you can see, the overall height of the bars increases from "Current" to "2080", indicating that there will be an increase in area that malaria could spread. However, there is a decrease in the dark pink bar height from "Current" to "2080," indicating that there will be a decrease in the strength of transmission in some areas.
Figure 3 from Ryan et al. 2015
Finding #2: Population at Risk
Researchers found that the populations with the highest risk for malaria transmission will change over the coming years. As depicted in the maps below, the current year-round, most suitable and highly populated area is the Ghana coast of western Africa. By 2080, it is expected that malaria transmission will no longer be year round in this area. Instead, the most suitable, year-round hotspot is predicted to shift to the Albertine Rift border of Western Uganda.
Change in transmission suitability and population
Figure 4 from Ryan et al. 2015
Potential population at risk for most suitable malaria transmission temperatures (R0 > 0 is greater or equal to 25%)
Finding #3: Current Monthly Malaria Transmission
The researchers used the model they created to visualize the current monthly suitability for possible malaria transmission around the world. However, these maps do not represent the actual areas where transmission is active. In other words, these maps illustrate areas where the climate is suitable for the Anopheles mosquito to live and transmit disease hypothetically, if not for insect control strategies and lack of the plasmodium in the population for example.
Side by Side Comparison
The slider below compares January vs July risk. As you may notice, the southern hemisphere has a greater risk of Malaria transmission in January while the northern hemisphere has a greater risk of transmission in July. Parts of the tropics, specifically northern South America and Sub-Saharan Africa support year round transmission.
Finding #4: Year Round Transmission Summary
The map below represents the risk for malaria transmission cumulatively, per year. As with many of the maps on this site, the deep red colors represent 12 months of potential transmission while the dark blue represents 1 month. Interact with the map to view risk for different areas around the world in greater detail.
World wide Malaria Risk in a year.
Malaria Risk in North America in a year.
Malaria Risk in the Southeastern USA in a year.