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Malaria is a serious and sometimes fatal disease caused by a parasite that commonly infects a certain type of mosquito which feeds on humans. Four kinds of malaria parasites have long been known to infect humans: Plasmodium falciparum, P. vivax, P. ovale, and P. malariae. Recently, it has been recognized that P. knowlesi, a type of malaria that naturally infects macaques in Southeast Asia, also infects humans, causing malaria that is transmitted from animal to human ("zoonotic" malaria). P. falciparum is the type of malaria that is most likely to result in severe infections and if not promptly treated, may lead to death. Although malaria can be a deadly disease, illness and death from malaria can usually be prevented.
About 1,500 cases of malaria are diagnosed in the United States each year. The vast majority of cases in the United States are in travelers and immigrants returning from parts of the world where malaria transmission occurs, including sub-Saharan Africa and South Asia.
The World Health Organization estimates that in 2008, 190 - 311 million clinical cases of malaria occurred, and 708,000 - 1,003,000 people died of malaria, most of them children in Africa.
Symptoms of malaria include fever and flu-like illness, including shaking chills, headache, muscle aches, and tiredness. Nausea, vomiting, and diarrhea may also occur. Malaria may cause anemia and jaundice (yellow coloring of the skin and eyes) because of the loss of red blood cells. If not promptly treated, the infection can become severe and may cause kidney failure, seizures, mental confusion, coma, and death.
For most people, symptoms begin 10 days to 4 weeks after infection, although a person may feel ill as early as 7 days or as late as 1 year later. Two kinds of malaria, P. vivax and P. ovale, can occur again (relapsing malaria). In P. vivax and P. ovale infections, some parasites can remain dormant in the liver for several months up to about 4 years after a person is bitten by an infected mosquito. When these parasites come out of hibernation and begin invading red blood cells ("relapse"), the person will become sick.
The surest way for you and your health-care provider to know whether you have malaria is to have a diagnostic test where a drop of your blood is examined under the microscope for the presence of malaria parasites. If you are sick and there is any suspicion of malaria (for example, if you have recently traveled in a country where malaria transmission occurs), the test should be performed without delay.
The disease should be treated early in its course, before it becomes serious and life-threatening. Several good antimalarial drugs are available, and should be taken early on. The most important step is to think about malaria if you are presently in, or have recently been in, an area with malaria, so that the disease is diagnosed and treated right away.
Malaria can be cured with prescription drugs. The type of drugs and length of treatment depend on the type of malaria, where the person was infected, their age, whether they are pregnant, and how sick they are at the start of treatment. See the CDC Guidelines for Treatment of Malaria.