Malaria

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Malaria is a life-threatening mosquito-borne parasitic disease caused by Plasmodium species, with P. falciparum and P. vivax representing the greatest threat. In 2024, an estimated 282 million cases and 610,000 deaths occurred globally, concentrated predominantly in the WHO African Region, where children under five bear a disproportionate burden of mortality.

Definition

Malaria is an acute febrile illness caused by Plasmodium parasites, transmitted through the bites of infected female Anopheles mosquitoes. Five parasite species cause malaria in humans, with Plasmodium falciparum and Plasmodium vivax posing the greatest threat due to their association with severe disease and mortality. The disease is both preventable and curable, though prompt diagnosis and effective treatment are essential to prevent progression to fatal outcomes.

Clinical features

Malaria typically presents with fever, headache, and chills, appearing 10–15 days after an infective mosquito bite. Early symptoms may be mild and nonspecific, complicating recognition. Uncomplicated cases can progress to severe illness within 24 hours if caused by P. falciparum, potentially resulting in death. Severe manifestations include fatigue, confusion, seizures, coma, jaundice, and respiratory distress. Children frequently develop severe anaemia and respiratory compromise. Without treatment, recurrence may occur months later. Survivors develop partial immunity that wanes without continued exposure.

Epidemiology

In 2024, an estimated 282 million malaria cases and 610,000 deaths occurred across 80 countries. The WHO African Region accounted for approximately 95% of both cases (265 million) and deaths (579,000). Children under five years of age represented about 75–76% of all malaria deaths in the African Region, with Nigeria, the Democratic Republic of the Congo, and Niger contributing over half of regional mortality. While sub-Saharan Africa bears the greatest burden, significant transmission persists across South-East Asia, Eastern Mediterranean, Western Pacific, and the Americas. Nearly half of the global population was at risk in 2024.

Transmission

Malaria is transmitted exclusively through the bites of infected female Anopheles mosquitoes, with over 400 species identified and approximately 40 serving as competent vectors. The disease is not contagious and does not spread person-to-person. Rare transmission can occur via blood transfusion or contaminated needles. Transmission intensity varies geographically and seasonally, with risk highest during rainy seasons in tropical countries.

Risk groups

Children under five years of age face the highest risk of severe disease and death, accounting for approximately three-quarters of malaria mortality in the African Region. Infants, pregnant women and girls, travelers lacking immunity, and people living with HIV or AIDS are also at elevated risk for severe infection. Immunologically naive populations entering endemic areas demonstrate particular vulnerability.

Prevention

Malaria prevention relies on avoiding mosquito bites through insecticide-treated nets and indoor residual spraying, the two core vector control interventions. Chemoprophylaxis is recommended for travelers to endemic areas. Emerging insecticide resistance among Anopheles mosquitoes threatens control progress, though new generation nets offering improved protection are becoming more widely available. The invasive vector Anopheles stephensi presents an additional challenge for malaria control in Africa.

Surveillance note

Malaria surveillance should account for the pronounced geographic concentration of burden in sub-Saharan Africa and the elevated mortality risk among children under five. Seasonal transmission patterns and the presence of drug-resistant parasites may influence case detection and reporting. The disease's nonspecific early symptoms necessitate laboratory confirmation for accurate surveillance. Trends in insecticide resistance and vector species composition warrant ongoing monitoring.

References