From the data on the previous page, we can conclude that temperature increases are very likely an influencing factor in the observed increase in cases of malaria. However, the question of how climate change affects the geographical distribution of disease is a tricky one. Although the model suggests that the conditions for mosquitos and malarial parasites are becoming more favourable in some areas, other factors also influence the spread of disease and must be accounted for.

Question: Name three factors aside from climate change that could influence the rate of malaria infection.

Possible answers include:

• Health care: In Africa, the availability and quality of healthcare services is not the same in all regions. During times of civil unrest, medical services often decline because they are dependent on funding from the government or outside sources. The quality of healthcare can also decrease after a large disturbance or natural disaster. In areas where high quality healthcare is available, proper treatment reduces the number of deaths due to malaria.
• Malaria prevention: The number of people infected by malaria can be reduced through the use of insecticide-treated nets and mosquito repellent sprays. Treating babies with sulfadoxinepyrimethamine (SP) at the time of routine vaccinations has been shown to reduce the frequency of clinical malaria episodes by 60%.
• Human immunity: Human populations in areas where malaria is an endemic disease often have higher percentages of the sickle-cell trait. This trait increases an individual's resistance to malaria. People who move from low-risk to high-risk areas are often more likely to contract malaria because they have a smaller chance of carrying the sickle-cell trait. Individuals living in cities are often less exposed to malarial mosquitos than those in rural areas. People are also more prone to disease during times of stress, such as war or famine, when immunity is decreased.
• Drug Resistance: In some areas, malaria has become resistant to chloroquine, the cheapest and most commonly used anti-malarial drug. Resistance is spreading in almost all countries where malaria is an endemic disease.

Question: Can the increased frequency of malaria in previously unaffected African areas be attributed to these factors?