Malaria is a life-threatening disease caused by Plasmodium parasites, transmitted to people through the bites of infected female Anopheles mosquitoes. While a global public health issue, its impact is uneven, with the vast majority of cases and deaths occurring on the African continent.
Africa’s Unique Vulnerability to Malaria
Africa is disproportionately affected by malaria, accounting for about 94% of cases and 95% of deaths globally. A primary driver for this is the environment across sub-Saharan Africa. The warm, humid climate allows for the year-round survival and breeding of the Anopheles mosquito, which acts as the vector for the parasite.
The issue is compounded by the prevalence of the Anopheles gambiae mosquito species. These mosquitoes are highly efficient at transmitting malaria due to their long lifespan and strong preference for biting humans over other animals. This combination of an ideal climate and an effective vector means populations are exposed to infectious bites more frequently.
Plasmodium falciparum, the most virulent of the five human-infecting species, is the dominant parasite in Africa. This species multiplies rapidly in the bloodstream, causing severe anemia and clogging small blood vessels. These effects can lead to cerebral malaria and other life-threatening complications.
Socioeconomic and health system challenges exacerbate these vulnerabilities. Widespread poverty can limit a household’s ability to afford preventive measures or access timely medical care. Additionally, strained public health infrastructure makes it difficult to sustain vector control programs or keep clinics stocked with diagnostic tests and medicines.
Malaria’s Path Through the Human Body
The parasite’s journey begins when an infected Anopheles mosquito bites a person, injecting sporozoites into the bloodstream. These sporozoites travel to the liver, where they invade cells and multiply silently for one to two weeks. During this incubation period, the person experiences no symptoms.
Once matured, the parasites, now called merozoites, burst from the liver and enter the bloodstream to invade red blood cells. Inside, they multiply until they rupture the cells, releasing more merozoites to infect other red blood cells. This cyclical process of invasion and rupture causes the symptoms of malaria.
Initial symptoms appear 7 to 15 days after the bite and resemble the flu, including fever, chills, and headaches. If a P. falciparum infection is not treated within 24 hours, it can progress to severe malaria. This can cause severe anemia, respiratory distress, and cerebral malaria, where clogged capillaries in the brain lead to seizures, coma, and death.
Certain groups are more vulnerable to severe outcomes. Children under five are at the highest risk as they lack partial immunity, accounting for about 76% of malaria deaths in Africa. Pregnant women are also highly susceptible, as the infection can cause severe anemia in the mother and low birth weight in the infant due to placental malaria.
Diagnosis in Africa relies on two primary methods. The first is microscopy to identify the parasite in a blood smear, and the second is Rapid Diagnostic Tests (RDTs). RDTs are more common and work by detecting parasite-specific antigens in a drop of blood.
Established Prevention and Control Strategies
Malaria control in Africa has long focused on targeting the mosquito vector. The two most effective strategies are insecticide-treated nets (ITNs) and indoor residual spraying (IRS). ITNs are insecticide-laced nets hung over beds that create a protective barrier at night when Anopheles mosquitoes are most active. The insecticide also kills mosquitoes that land on the net, reducing the local mosquito population.
IRS involves coating the inside walls of homes with a long-lasting insecticide, which kills mosquitoes that rest on the surfaces after feeding. High community coverage with IRS can significantly reduce transmission. The effectiveness of both ITNs and IRS is threatened by the spread of insecticide resistance in mosquitoes.
Chemoprevention uses antimalarial medicines to protect vulnerable populations. One strategy is Seasonal Malaria Chemoprevention (SMC), used for children in regions with highly seasonal transmission like the Sahel. During the rainy season, eligible children receive a monthly course of antimalarial treatment for three to four months.
Another approach is Intermittent Preventive Treatment in pregnancy (IPTp). This involves giving an antimalarial drug to pregnant women at scheduled antenatal visits after the first trimester. This treatment clears existing parasites and prevents new infections, protecting both the mother and the unborn child.
Advanced Treatments and the Dawn of a Vaccine Era
When infection occurs, rapid treatment is necessary. The standard for uncomplicated P. falciparum malaria is Artemisinin-based Combination Therapies (ACTs). ACTs combine two drugs: a fast-acting artemisinin derivative to quickly reduce parasites and a longer-acting partner drug to clear the rest.
This combination strategy helps protect against drug resistance, as a parasite resistant to one drug will likely be killed by the other. However, resistance to ACTs has emerged in some regions. This poses a serious threat to malaria control and requires ongoing research for new antimalarial compounds.
A major development in malaria control is the arrival of vaccines. In 2021, the World Health Organization recommended the RTS,S/AS01 vaccine for children in high-transmission regions, the first ever for a parasitic disease. The RTS,S vaccine prompts the immune system to build antibodies against the P. falciparum parasite, reducing malaria cases and severe disease in young children.
A second vaccine, R21/Matrix-M, was recommended by the WHO in October 2023. Having two vaccines is expected to increase supply and make rollouts more feasible across Africa. These vaccines are being integrated into childhood immunization programs alongside existing tools like bed nets, and are anticipated to save tens of thousands of young lives annually.