Malaria

About Malaria

Malaria is a common infection in hot, tropical areas but can also occur (very rarely) in temperate climates.

It is caused by any of four single-celled parasites of the Plasmodium species, which are carried by mosquitoes infected from biting someone who already has the disease. Malaria is then transmitted to other people when infected mosquitoes bite them. Rarely, it is passed from person to person (from mother to child in "congenital malaria," or through blood transfusion, organ donation, or shared needles).

Worldwide, 300-500 million people are infected with malaria each year. Most cases occur in sub-Saharan Africa, with approximately 2 million people dying there each year. Malaria is rare in the United States, with only about 1,300 cases reported each year over the last 10 years. Most of these cases occurred in travelers, military personnel, and immigrants who had become infected by malaria parasites outside the United States.

Signs and Symptoms

A child with early symptoms of malaria may be irritable and drowsy, with poor appetite and trouble sleeping. These symptoms are usually followed by chills, then a fever with rapid breathing. The fever may either gradually increase over 1 to 2 days or may rise very suddenly to 105º Fahrenheit (40.6º Celsius) or above. Then, as fever ends and body temperature quickly returns to normal, the child has an intense episode of sweating.

The same pattern of symptoms - chills, fever, sweating - may repeat at intervals of 2 or 3 days, depending on which particular species of malaria parasite is causing the infection. Because the initial symptoms are not specific and can be mistaken for other diseases, it can be difficult to diagnose. In countries where the disease is seen a lot, it's not uncommon for doctors to treat people for malaria who have fever of no obvious cause without getting laboratory confirmation.

Other symptoms of malaria include headache, nausea, aches and pains all over the body (especially the back and abdomen), and an abnormally large spleen. When malaria affects the brain, a child may have convulsions or lose consciousness. If malaria affects the kidneys, the amount of urine produced by the child may be abnormally low. In falciparum malaria , caused by the Plasmodium falciparum parasite, the episode of fever and chills is especially intense, and this variety may be fatal in about 20% of cases.

Once malaria parasites enter the bloodstream, they travel to the liver and multiply. Every few days, thousands of parasites are released from the liver into the blood, where they destroy red blood cells. Some parasites also remain in the liver and continue to multiply, releasing more parasites into the blood every few days.

The incubation period for malaria is the time between the mosquito bite and the release of parasites from the liver. This varies, depending on which malaria parasite is causing the disease. In general, it can range from 10 days to a month.

With treatment, malaria can usually be cured in about 2 weeks. Without treatment, it can be fatal, especially in children who are poorly nourished.

Prevention

Health authorities try to prevent malaria by using mosquito-control programs aimed at killing mosquitoes that carry the disease. If you travel to an area of the world with a high risk for malaria, you can install window screens, use insect repellents, and place mosquito netting over beds. Insecticide-impregnated bed netting has successfully reduced the number of malarial deaths among African children.

Check with your doctor before visiting any tropical or subtropical area at high risk for malaria. Your doctor can give your family anti-malarial drugs to prevent the disease. Several malaria vaccines are currently being developed and tested across the world, but because the malaria parasite has a complicated life cycle, it is a difficult vaccine to develop.

Diagnosis and Treatment

Doctors diagnose malaria by using special blood tests. A blood sample is sent to the laboratory and checked under a microscope for malaria parasites, which may be seen inside infected red blood cells.

Doctors treat malaria with anti-malarial drugs, such as chloroquine or quinine, given by mouth, by injection, or intravenously (into the veins). Depending on the type of parasite causing the malaria, a person can be treated as an outpatient over a few days or may require hospitalization with IV medication. Doctors also watch for signs of dehydration, convulsions, anemia, and other complications that can affect the brain, kidneys, or spleen. The patient may require fluids, blood transfusions, and breathing assistance.

Malaria is a leading cause of death worldwide. If diagnosed early and treated, it can be cured. However, many people who live in areas where malaria is common get repeated infections and never really recover between episodes of illness.

Reviewed by: Joel Klein, MD
Date reviewed: April 2009