Malaria is a life-threatening disease caused by parasites that are transmitted to people through the bites of infected female Anopheles mosquitoes.
There are 5 parasite species that cause malaria in humans, and 2 of these species – P. falciparum and P. vivax – pose the greatest threat.
P. falciparum is the most prevalent malaria parasite on the African continent. It is responsible for most malaria-related deaths globally.
P. vivax is the dominant malaria parasite in most countries outside of sub-Saharan Africa.
Malaria parasite - Plasmodium falciparum
Malaria is preventable and curable, and increased efforts are dramatically reducing the malaria burden in many places.
Between 2010 and 2015, malaria incidence among populations at risk (the rate of new cases) fell by 21% globally.
In that same period, malaria mortality rates among populations at risk fell by 29% globally among all age groups, and by 35% among children under 5.
The WHO African Region carries a disproportionately high share of the global malaria burden. In 2015, the region was home to 90% of malaria cases and 92% of malaria deaths.
Some population groups are at considerably higher risk of contracting malaria, and developing severe disease, than others.
These include infants, children under 5 years of age, pregnant women and patients with HIV/AIDS, as well as non-immune migrants, mobile populations and travellers. Symptoms
In a non-immune individual, symptoms usually appear 10–15 days after the infective mosquito bite. The first symptoms – fever, headache, and chills– may be mild and difficult to recognize as malaria.
If not treated within 24 hours, P. falciparum malaria can progress to severe illness, often leading to death.
Children with severe malaria frequently develop one or more of the following symptoms: severe anaemia, respiratory distress in relation to metabolic acidosis, or cerebral malaria.
In adults, multi-organ involvement is also frequent. In malaria endemic areas, people may develop partial immunity, allowing asymptomatic infections to occur.
Transmission
Anopheles mosquitoes lay their eggs in water, which hatch into larvae, eventually emerging as adult mosquitoes.
The female mosquitoes seek a blood meal to nurture their eggs. Each species of Anopheles mosquito has its own preferred aquatic habitat;
For example, some prefer small, shallow collections of fresh water, such as puddles and hoof prints, which are abundant during the rainy season in tropical countries.
Transmission also depends on climatic conditions that may affect the number and survival of mosquitoes, such as rainfall patterns, temperature and humidity.
In many places, transmission is seasonal, with the peak during and just after the rainy season.
Human immunity is another important factor, especially among adults in areas of moderate or intense transmission conditions.
Partial immunity is developed over years of exposure, and while it never provides complete protection, it does reduce the risk that malaria infection will cause severe disease.
For this reason, most malaria deaths in Africa occur in young children, whereas in areas with less transmission and low immunity, all age groups are at risk.
Prevention
People at risk of malaria should sleep under a Long-lasting mosquito insecticidal nets (LLIN) every night, and that the net is properly maintained.
Indoor residual spraying (IRS) with insecticides is a powerful way to rapidly reduce malaria transmission.
Antimalarial medicines can also be used to prevent malaria.
The best available treatment, particularly for P. falciparum malaria, is artemisinin-based combination therapy (ACT).
