Malaria

Malaria is a common infection in hot, tropical areas but can also occur (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 they are bitten by the infected mosquitoes. It is rarely 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 105 degrees Fahrenheit (40.6 degrees 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.