Malaria is caused by a type of parasite (an organism that lives and feeds off another organism) known as plasmodium. There are hundreds of different types of plasmodium, but only four of them cause malaria in humans.

The four types of plasmodium parasite include:

• Plasmodium falciparum - this is the only malignant form of malaria, and is predominantly found in Africa. This parasite causes the most severe symptoms and results in the most fatalities.
• Plasmodium vivax - a benign type of parasite found mainly in Asia. It produces less severe symptoms than plasmodium falciparum, but can stay in the liver for up to three years, which can result in relapses of the condition.
• Plasmodium ovale - a benign parasite that is usually found in Africa. This type of parasite can stay in your blood for several years without producing any symptoms.
• Plasmodium malarie - this benign parasite is relatively rare and is usually only found in West Africa.

How does the parasite spread?

The plasmodium parasite is usually transmitted by a particular species of mosquito, known as the anopheles mosquito. If a female of the species bites a person infected with malaria, the mosquito can then carry the parasite and spread it to others when it bites and feeds from a person's blood.

When the plasmodium parasite enters your blood stream, it travels to the liver and then re-enters the blood stream where it is able to invade red blood cells. Eventually, the infected red blood cells burst and, when they do, they release even more of the tiny parasites into the blood. The infected cells tend to burst every 48-72 hours. Each time they burst, you will usually experience an attack of chills, fever and sweating.

Pregnancy and malaria

Research suggests that if you are pregnant, you are more at risk of catching malaria than normal. This is because your immune system can be weaker during pregnancy, which means your body is less able to fight off bacteria and infection. If you are pregnant and have malaria, you may pass the infection on to your baby. See the 'treatment' section for details of the malaria medicines that are safe to use during pregnancy.