Malaria (mah-LAIR-e-uh) is a disease caused by a parasite that is spread to humans by the bite of an infected mosquito.
Malaria, which literally means bad air, was once thought to be spread in the air around stagnant marshes. It was later discovered that mosquitoes, particularly female Anopheles (a-NOH-fel-eez) mosquitoes, spread the parasites that cause malaria. Four different species of a parasite in the genus Plasmodium (plaz-MO-dee-um) cause malaria. They are falciparum (fal-SIP-ar-um), malariae (mah-LAIR-e-eye), ovale (o-VAL-e), and vivax (VY-vax). Of the four, P. falciparum is the most common and the most deadly. Plasmodium requires time in both the mosquito vector * and human host * to complete its life cycle.
Forty percent of the world's population is at risk for contracting malaria from infected mosquitoes, primarily in tropical and subtropical regions. Worldwide, there are 300 to 500 million cases of malaria and more than 1 million deaths from malaria each year. More than 90 percent of all malaria deaths occur in sub-Saharan Africa, a vast area south of the Sahara Desert, and 75 percent of deaths occur in children. P. falciparum causes malaria in this region, and poverty, poor nutrition, and poor access to health care all contribute to the high death rate. Malaria is increasingly common in Central and South America, Asia, the Middle East, and the Pacific Islands. About 1,200 cases of malaria are diagnosed in the United States each year, mostly in recent immigrants or travelers from countries where malaria is found.
Mosquito control has virtually eliminated malaria in areas with temperate climates. However, the disease has made a comeback as mosquitoes have become resistant to insecticides and Plasmodium has become resistant to medications used to treat malaria.
Malaria is not passed directly from one person to another. Mosquitoes spread the disease. When a mosquito bites an infected person, it ingests malaria parasites contained in that person's blood. The parasites need an incubation * period of about one week in the mosquito before the mosquito can spread the disease when it bites another person. Once in a person's body, the parasites travel to the liver where they can remain dormant, or inactive, for months or even years. In the liver, the parasites grow and multiply and are then ready to move into the body's red blood cells, where they continue to grow until the red blood cells burst, freeing more parasites to attack more blood cells. The parasite can be ingested by a mosquito and spread to another person only during the time that Plasmodium is in the blood.
Under the microscope, a blood sample from a person who has malaria will show one of the four species of Plasmodium parasites within the red blood cells. Malaria is treated with antimalarial drugs, many of them derived from quinine, which is found naturally in the bark of the cinchona tree from Peru. Which drug is chosen to treat a patient depends on the parasite causing the infection, the severity of symptoms, the age of the patient, and whether the parasite is resistant to certain drugs. Some patients may need intensive hospital care.
Treatment can last several weeks or months. In some infections, the parasite can remain dormant in the liver for months or years, and the disease may return even after treatment. Destruction of red blood cells in cases of malaria can result in anemia * and jaundice * * problems, seizures * , mental confusion, coma * , and death; malaria is fatal in 1 in 500 cases. Children and pregnant women are particularly vulnerable to complications. Infected pregnant women are at risk for miscarriage * , premature labor * , and stillbirth * , and anemia in children can have long-term effects on growth and development.
In areas where malaria is endemic * , people can avoid being bitten by mosquitoes by wearing long-sleeved shirts and long pants, using insect repellent, and staying in a screened or air-conditioned room from dusk to dawn when mosquitoes are most active. Bed nets treated with certain insecticides repel mosquitoes for 6 to 12 months.
Anyone traveling to a malaria-endemic area should visit a doctor four to six weeks prior to travel to receive the appropriate vaccinations for certain tropical infections and proper prescriptions to prevent malaria. This precaution applies to people who grew up in a malaria-endemic area and have lived elsewhere for a period of time.
As of 2015, researchers were close to receiving full approval for a malaria vaccine, designed specifically to combat malaria infection in children in Africa. The vaccine requires booster shots over time, which can be challenging to achieve in some parts of Africa. As a result, bed netting is still the most effective preventive approach.
See also Parasitic Diseases: Overview • Travel-Related Infections: Overview
Masterson, Karen M. The Malaria Project: The U.S. Government's Secret Mission to Find a Miracle Cure. New York: New American Library, 2014.
Packard, Randall M. The Making of a Tropical Disease: A Short History of Malaria. Baltimore, MD: Johns Hopkins University Press, 2011.
Walsh, Fergus. “Malaria Vaccine Gets ‘Green Light.’” BBC News, July 24, 2015. http://www.bbc.com/news/health-33641939 (accessed October 26, 2015).
World Health Organization. “World Malaria Report 2014.” http://www.who.int/malaria/publications/world_malaria_report_2014/report/en/ (accessed November 17, 2015).
Centers for Disease Control and Prevention. “Malaria.” http://www.cdc.gov/malaria (accessed October 26, 2015).
MedlinePlus. “Malaria.” U.S. National Library of Medicine, National Institutes of Health. https://www.nlm.nih.gov/medlineplus/malaria . html (accessed November 17, 2015).
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Centers for Disease Control and Prevention. 1600 Clifton Rd., Atlanta, GA 30329. Toll-free: 800-232-4636. Website: http://www.cdc.gov (accessed November 17, 2015).
World Health Organization. Avenue Appia 20, 1211 Geneva 27, Switzerland. Telephone: 41-22-791-2111. Website: http://www.who.int (accessed October 26, 2015).
* vector (VEK-tor) is an animal or insect that carries a diseasecausing organism and transfers it from one host to another.
* host is an organism that provides another organism (such as a parasite or virus) with a place to live and grow.
* incubation (ing-kyoo-BAY-shun) is the period of time between infection by a germ and when symptoms first appear. Depending on the germ, this period can be from hours to months.
* nausea (NAW-zha) refers to a feeling of being sick to one's stomach or needing to vomit.
* diarrhea (di-ah-RE-a) refers to frequent, watery stools (bowel movements).
* anemia (uh-NEE-me-uh) is a blood condition in which there is a decreased hemoglobin in the blood and, usually, fewer than normal numbers of red blood cells.
* jaundice (JON-dis) is a yellowing of the skin, and sometimes the whites of the eyes, caused by a buildup in the body of bilirubin, a chemical produced in and released by the liver.
* toxins are substances that cause harm to the body.
* premature labor is when a is born before it has reached term.
* stillbirth is the birth of a dead fetus.
* endemic (en-DEH-mik) describes a disease or condition that present in a population or geographic area at all times.
* kidney is one of the pair of organs that filter blood and remove waste products and excess water from the body the form of urine.
* seizures (SEE-zhurs), also called convulsions, are sudden bursts of disorganized electrical activity that interrupt the normal functioning of the brain, often leading to uncontrolled movements the body and sometimes a temporary change in consciousness.
* miscarriage (MIS-kare-ij) is end of a pregnancy through the death of the embryo or before birth.
* coma (KO-ma) is an unconscious state, like a very deep sleep. A person in a coma cannot be awakened, and cannot move, see, speak, or hear.