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The malaria cycle

Child in bed

How malaria spreads – the cycle of infection

Malaria is a disease caused by a parasite called Plasmodium. It is transmitted exclusively through the bites of female Anopheles mosquitoes. When an infected mosquito bites a human, the parasites enter the blood. Within 30 minutes they infect the liver. Between six and nine days later, the parasites leave the liver and enter the bloodstream where they invade red blood cells. As the parasites multiply, the red blood cells burst, releasing thousands more parasites into the bloodstream where they infect other blood cells. It is at this point that the person will suffer from high fever, chills, nausea and anemia. When another mosquito bites the infected human, the parasite is transferred to that mosquito. While in the second mosquito, the malaria parasite goes through several stages of growth, which takes between 10 and 21 days, depending on the parasite species and the temperature. When the second mosquito bites someone else, the cycle begins again.

Why species and climate matter – the perfect storm

About 20 different Anopheles species are locally important around the world. Some prefer to bite animals, while others prefer to bite humans. Some have longer life spans, which gives the malaria parasite the time it needs within the mosquito to develop. If the mosquito dies, the parasite dies with it. The hotter the climate, the less time it takes for the parasite to develop. In sub-Saharan Africa, the Anopheles gambiae mosquito both prefers to bite humans and has a longer life span. The climate also allows the mosquito to survive year-round – and the heat helps the parasite to develop quickly. As if this weren’t sufficient, Africa is also home to the deadliest form of the malaria parasite: Plasmodium falciparum. It is for all these reasons that an overwhelming 90% of malaria deaths occur in Africa.

The infographic shows how malaria infects humans.