Malaria, the world's most important parasitic infectious disease, is transmitted by mosquitoes which breed in fresh or occasionally brackish water.

The symptoms of malaria include fever, chills, headache, muscle aches, tiredness, nausea and vomiting, diarrhoea, anaemia, and jaundice (yellow colouring of the skin and eyes). Convulsions, coma, severe anaemia and kidney failure can also occur. The severity and range of symptoms depend on the specific type of malaria. In certain types, the infection can remain inactive for up to five years and then recur. In areas with intense malaria transmission, people can develop protective immunity after repeated infections. Without prompt and effective treatment, malaria can evolve into a severe cerebral form followed by death. Malaria is among the five leading causes of death in under-5-year-old children in Africa.

Malaria is caused by four species of Plasmodium parasites (P. falciparum, P. vivax, P. ovale, P. malariae). People get malaria after being bitten by a malaria-infected Anopheles mosquito. Some female mosquitoes take their blood-meal at dusk and early evening, but others bite during the night or in the early hours of the morning. When a mosquito bites an infected person, it ingests malaria parasites with the blood. During a period of 8 to 35 days (depending on the ambient temperature), the parasite develops in the mosquito. The infective form (sporozoite) ends up in the salivary glands and is injected into the new human host at subsequent blood-meals. In the human host, the sporozoites migrate to the liver, multiply inside liver cells, and spread into the bloodstream. The liver phase can last between 8 days and several months, depending on the malaria species. Their growth and multiplication takes place inside red blood cells. Clinical symptoms occur when the red blood cells break up. If this happens in large numbers, the person experiences the characteristic intermittent fevers of the disease. The released parasites invade other blood cells. Most people begin feeling sick 10 days to 4 weeks after being infected.

WHO's Strategy for Malaria Control, which forms the basis of the Roll Back Malaria initiative, identifies four main interventions:

• Reducing mortality, particularly among children, by early case-detection and prompt treatment with effective anti-malarial drugs
• Promoting the use of insecticide-treated bed nets, especially by children and pregnant women
• Prevention of malaria in pregnancy by applying intermittent preventive therapy
• Ensuring early detection and control of malaria epidemics, especially in emergency situations.

Source: WHO