FAQS

Definition of the disease

MALARIA is a life-threatening parasitic disease transmitted by mosquitoes. It was once thought that the disease came from fetid marshes, hence the name ‘mal aria,’ (bad air). In 1880, scientists discovered the real cause of malaria—a one-cell parasite called plasmodium. Later they discovered that the parasite is transmitted from person to person through the bite of a female Anopheles mosquito, which requires blood to nurture her eggs.

Transmission

There are four types of human malaria— Plasmodium vivax, P. malariae, P. ovale and P. falciparum. P. vivax and P. falciparum are the most common and falciparum the most deadly type of malaria infection. Plasmodium falciparum malaria is most common in Africa, south of the Sahara, accounting in large part for the extremely high mortality in this region. There are also worrying indications of the spread of P. falciparum malaria into new regions of the world and its reappearance in areas where it had been eliminated.

The malaria parasite enters the human host when an infected Anopheles mosquito takes a blood meal. Inside the human host, the parasite undergoes a series of changes as part of its complex life-cycle. Its various stages allow plasmodia to evade the immune system, infect the liver and red blood cells, and finally develop into a form that is able to infect a mosquito again when it bites an infected person. Inside the mosquito, the parasite undergoes more changes until it reaches the stage where it can again infect a human host when the mosquito takes her next blood meal, 10 to 14 or more days later.

Symptoms

Malaria symptoms appear about 9 to 14 days after the infectious mosquito bite, although this varies with different plasmodium species. Typically, malaria produces fever, headache, vomiting and other flu-like symptoms. If drugs are not available for treatment or the parasites are resistant to them, the infection can progress rapidly to become life-threatening. Malaria can kill by infecting and destroying red blood cells (anaemia) and by clogging the capillaries that carry blood to the brain (cerebral malaria) or other vital organs.

Prevalence

Today approximately 40% of the world's population—mostly those living in the world's poorest countries—is at risk of malaria. The disease was once more widespread but it was successfully eliminated from many countries with temperate climates during the mid 20th century. Today malaria is found throughout the tropical and sub-tropical regions of the world and causes more than 300 million acute illnesses and at least one million deaths annually.

Ninety per cent of deaths due to malaria occur in Africa, south of the Sahara—mostly among young children. Malaria kills an African child every 30 seconds. Malaria is Africa's leading cause of under-five mortality (20%) and constitutes 10% of the continent's overall disease burden. It accounts for 40% of public health expenditure, 30-50% of inpatient admissions, and up to 50% of outpatient visits in areas with high malaria transmission. Many children who survive an episode of severe malaria may suffer from learning impairments or brain damage. Pregnant women and their unborn children are also particularly vulnerable to malaria, which is a major cause of perinatal mortality, low birth weight and maternal anaemia

Treatment and Drug Resistance

One of the greatest challenges facing Africa in the fight against malaria is drug resistance. Resistance to chloroquine, the cheapest and most widely used antimalarial, is common throughout Africa (particularly in southern and eastern parts of the continent). Resistance to sulfadoxine-pyrimethamine (SP), often seen as the first and least expensive alternative to chloroquine, is also increasing in east and southern Africa. As a result of these trends, many countries are having to change their treatment policies and use drugs which are more expensive, including combinations of drugs, which it is hoped will slow the development of resistance.

Epidemics

EPIDEMICS occur when malaria attacks vulnerable populations with little or no immunity. In such situations, people of all age groups are at risk of death or severe disease. The populations most at risk of epidemics are those living in highlands, arid and desert-fringe zones, as well as those living in areas where successful control measures have not been consolidated or maintained.

There are two categories of factors which may precipitate a malaria epidemic: natural (climatic variations, natural disasters), and man-made (conflict and war, agricultural projects, dams, mining, logging). Many of these factors modify the physical environment in some way, leading to an increase in the capacity of mosquitoes to transmit malaria. Some factors also result in massive population movements that expose non-immune populations to malaria infection.

Epidemics of Plasmodium falciparum malaria, the most severe form of the disease, can be devastating if not controlled quickly. It is difficult to predict when and where such epidemics are going to occur because malaria epidemics tend to occur in populations not normally exposed to the disease, or who are exposed for only a short part of the year. As a result local health services are usually unprepared to predict, detect and control such epidemics in time, resulting in severe cases and high death rates.

Economic Effects and Challenges

Malaria, together with HIV/AIDS and TB, is one of the major public health challenges undermining development in the poorest countries in the world. Malaria parasites have become resistant to one drug after another and many insecticides are no longer useful against the mosquitoes which transmit the disease. Years of vaccine research have produced few hopeful candidates and although scientists are redoubling the search, an effective vaccine is at best years away. There is still no magic bullet for malaria and there is doubt that such a single solution will ever exist.

Roll Back Malaria

• Prompt access to treatment with effective up-to-date medicines saves lives
• Insecticide-treated mosquito nets (ITNs) reduce malaria transmission and child deaths.
• Prevention and control of malaria in pregnant women results in improvement in maternal health, infant health and survival
• Malaria epidemic and emergency response

Source: WHO

MALARIA UPDATES
2002
2001

DRUGS & TREATMENT

Special Coverage: AFRICA MALARIA DAY, APRIL 25

Outbreaks