Malaria
Malaria is a mosquito-borne infectious disease that affects vertebrates.[6][7][3] Human malaria causes symptoms that typically include fever, fatigue, vomiting, and headaches.[1][8] In severe cases, it can cause jaundice, seizures, coma, or death.[1][9] Symptoms usually begin 10 to 15 days after being bitten by an infected Anopheles mosquito.[10][4] If not properly treated, people may have recurrences of the disease months later.[3] In those who have recently survived an infection, reinfection usually causes milder symptoms.[1] This partial resistance disappears over months to years if the person has no continuing exposure to malaria.[1]
For other uses, see Malaria (disambiguation).Malaria
Fever, vomiting, headache, yellow skin[1]
10–15 days post exposure[3]
Plasmodium transmitted to humans by Anopheles mosquitoes[1][4]
Examination of the blood, antigen detection tests[1]
Mosquito nets, insect repellent, mosquito control, medications[1]
247 million (2021)[5]
619,000 (2021)[5]
Human malaria is caused by single-celled microorganisms of the Plasmodium group.[10] It is spread exclusively through bites of infected female Anopheles mosquitoes.[10][11] The mosquito bite introduces the parasites from the mosquito's saliva into a person's blood.[3] The parasites travel to the liver, where they mature and reproduce.[1] Five species of Plasmodium commonly infect humans.[10] The three species associated with more severe cases are P. falciparum (which is responsible for the vast majority of malaria deaths), P. vivax, and P. knowlesi (a simian malaria that spills over into thousands of people a year).[12][13] P. ovale and P. malariae generally cause a milder form of malaria.[1][10] Malaria is typically diagnosed by the microscopic examination of blood using blood films, or with antigen-based rapid diagnostic tests.[1] Methods that use the polymerase chain reaction to detect the parasite's DNA have been developed, but they are not widely used in areas where malaria is common, due to their cost and complexity.[14]
The risk of disease can be reduced by preventing mosquito bites through the use of mosquito nets and insect repellents or with mosquito-control measures such as spraying insecticides and draining standing water.[1] Several medications are available to prevent malaria for travellers in areas where the disease is common.[3] Occasional doses of the combination medication sulfadoxine/pyrimethamine are recommended in infants and after the first trimester of pregnancy in areas with high rates of malaria.[3] As of 2023, two malaria vaccines have been endorsed by the World Health Organization.[15] The recommended treatment for malaria is a combination of antimalarial medications that includes artemisinin.[16][5][1][3] The second medication may be either mefloquine, lumefantrine, or sulfadoxine/pyrimethamine.[17] Quinine, along with doxycycline, may be used if artemisinin is not available.[17] In areas where the disease is common, malaria should be confirmed if possible before treatment is started due to concerns of increasing drug resistance.[3] Resistance among the parasites has developed to several antimalarial medications; for example, chloroquine-resistant P. falciparum has spread to most malarial areas, and resistance to artemisinin has become a problem in some parts of Southeast Asia.[3]
The disease is widespread in the tropical and subtropical regions that exist in a broad band around the equator.[18][1] This includes much of sub-Saharan Africa, Asia, and Latin America.[3] In 2022, some 249 million cases of malaria worldwide resulted in an estimated 608000 deaths, with 80 percent being five years old or less.[19] Around 95% of the cases and deaths occurred in sub-Saharan Africa. Rates of disease decreased from 2010 to 2014, but increased from 2015 to 2021.[5] According to UNICEF, nearly every minute, a child under five died of malaria in 2021,[20] and "many of these deaths are preventable and treatable".[21] Malaria is commonly associated with poverty and has a significant negative effect on economic development.[22][23] In Africa, it is estimated to result in losses of US$12 billion a year due to increased healthcare costs, lost ability to work, and adverse effects on tourism.[24]
Etymology[edit]
The term malaria originates from Mediaeval Italian: mala aria—"bad air", a part of miasma theory; the disease was formerly called ague or marsh fever due to its association with swamps and marshland.[25] The term appeared in English at least as early as 1768.[26] Malaria was once common in most of Europe and North America,[27] where it is no longer endemic,[28] though imported cases do occur.[29]
Other animals[edit]
While none of the main four species of malaria parasite that cause human infections are known to have animal reservoirs,[343] P. knowlesi is known to regularly infect both humans and non-human primates.[49] Other non-human primate malarias (particularly P. cynomolgi and P. simium) have also been found to have spilled over into humans.[344] Nearly 200 Plasmodium species have been identified that infect birds, reptiles, and other mammals,[345] and about 30 of them naturally infect non-human primates.[346] Some malaria parasites of non-human primates (NHP) serve as model organisms for human malarial parasites, such as P. coatneyi (a model for P. falciparum) and P. cynomolgi (a model for P. vivax). Diagnostic techniques used to detect parasites in NHP are similar to those employed for humans.[347] Malaria parasites that infect rodents are widely used as models in research, such as P. berghei.[348] Avian malaria primarily affects species of the order Passeriformes, and poses a substantial threat to birds of Hawaii, the Galapagos, and other archipelagoes. The parasite P. relictum is known to play a role in limiting the distribution and abundance of endemic Hawaiian birds. Global warming is expected to increase the prevalence and global distribution of avian malaria, as elevated temperatures provide optimal conditions for parasite reproduction.[349]