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Malaria is a mosquito-borne infectious disease of humans and other animals caused by parasitic protozoans (a group of single-celled microorganisms) belonging to the genus ''Plasmodium''.〔 Malaria causes symptoms that typically include fever, fatigue, vomiting, and headaches. In severe cases it can cause yellow skin, seizures, coma or death.〔 The disease is transmitted by the biting of mosquitos, and the symptoms usually begin ten to fifteen days after being bitten. If not appropriately treated, people may have recurrences of the disease months later.〔 In those who have recently survived an infection, re-infection typically causes milder symptoms. This partial resistance disappears over months to years if the person has no continuing exposure to malaria.〔 The disease is most commonly transmitted by an infected female ''Anopheles'' mosquito. The mosquito bite introduces the parasites from the mosquito's saliva into a person's blood.〔 The parasites travel to the liver where they mature and reproduce. Five species of ''Plasmodium'' can infect and be spread by humans.〔 Most deaths are caused by ''P. falciparum'' because ''P. vivax'', ''P. ovale'', and ''P. malariae'' generally cause a milder form of malaria.〔〔 The species ''P. knowlesi'' rarely causes disease in humans.〔 Malaria is typically diagnosed by the microscopic examination of blood using blood films, or with antigen-based rapid diagnostic tests.〔 Methods that use the polymerase chain reaction to detect the parasite's DNA have been developed, but are not widely used in areas where malaria is common due to their cost and complexity.〔 The risk of disease can be reduced by preventing mosquito bites by using mosquito nets and insect repellents, or with mosquito-control measures such as spraying insecticides and draining standing water.〔 Several medications are available to prevent malaria in travellers to areas where the disease is common. Occasional doses of the medication sulfadoxine/pyrimethamine are recommended in infants and after the first trimester of pregnancy in areas with high rates of malaria. Despite a need, no effective vaccine exists, although efforts to develop one are ongoing.〔 The recommended treatment for malaria is a combination of antimalarial medications that includes an artemisinin.〔〔 The second medication may be either mefloquine, lumefantrine, or sulfadoxine/pyrimethamine. Quinine along with doxycycline may be used if an artemisinin is not available.〔 It is recommended that in areas where the disease is common, malaria is confirmed if possible before treatment is started due to concerns of increasing drug resistance. 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.〔 The disease is widespread in the tropical and subtropical regions that exist in a broad band around the equator.〔 This includes much of Sub-Saharan Africa, Asia, and Latin America. Malaria is commonly associated with poverty and has a major negative effect on economic development.〔〔 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 negative effects on tourism.〔 The World Health Organization reports there were 198 million cases of malaria worldwide in 2013.〔 This resulted in an estimated 584,000 to 855,000 deaths, the majority (90%) of which occurred in Africa. ==Signs and symptoms== The signs and symptoms of malaria typically begin 8–25 days following infection;〔 however, symptoms may occur later in those who have taken antimalarial medications as prevention.〔 Initial manifestations of the disease—common to all malaria species—are similar to flu-like symptoms,〔 and can resemble other conditions such as sepsis, gastroenteritis, and viral diseases.〔 The presentation may include headache, fever, shivering, joint pain, vomiting, hemolytic anemia, jaundice, hemoglobin in the urine, retinal damage, and convulsions.〔 The classic symptom of malaria is paroxysm—a cyclical occurrence of sudden coldness followed by shivering and then fever and sweating, occurring every two days (tertian fever) in ''P. vivax'' and ''P. ovale'' infections, and every three days (quartan fever) for ''P. malariae''. ''P. falciparum'' infection can cause recurrent fever every 36–48 hours, or a less pronounced and almost continuous fever.〔 Severe malaria is usually caused by ''P. falciparum'' (often referred to as falciparum malaria). Symptoms of falciparum malaria arise 9–30 days after infection.〔 Individuals with cerebral malaria frequently exhibit neurological symptoms, including abnormal posturing, nystagmus, conjugate gaze palsy (failure of the eyes to turn together in the same direction), opisthotonus, seizures, or coma.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「malaria」の詳細全文を読む スポンサード リンク
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