Malaria

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What is malaria?

Malaria is a potentially serious disease caused by Plasmodium parasites. Plasmodia are transmitted between humans by the bite of an Anopheles mosquito that carries the parasite.

When Plasmodium parasites enter the human bloodstream, they travel to the liver and reproduce quickly. In most forms of malaria, some parasites also flow into the bloodstream and destroy red blood cells, which carry vital oxygen to the tissues of the body. This can result in anemia (a decreased number of red blood cells).

The parasites that stay in the liver continue to reproduce and periodically send more parasites into the bloodstream. This results in repeated attacks of flu-like symptoms each time new parasites are released into the blood. Attacks of malaria can recur for years if the disease is not diagnosed and treated. Eventually, the body’s immune system may develop a defense against the attacks, and they may become less severe in some people.

Malaria is most common in tropical and subtropical countries, where it is a serious public health threat. About half of the world’s population lives in areas at risk for malaria. Malaria is extremely rare in the United States, although the Anopheles mosquito is found in the western and southeastern part of the country. Mosquito control programs have essentially wiped out the disease in the United States. Most cases in the United States occur in people who have traveled outside the country to high-risk areas.

Malaria is a serious disease that can lead to complications, such as anemia and falciparum malaria, which is life threatening. Malaria is preventable with medications, so it is important to seek medical care before traveling to a subtropical or tropical area of the world where the disease is common.

What are the symptoms of malaria?

The signs and symptoms of malaria are the result of the reproduction of Plasmodium parasites in the liver and their spread into the bloodstream. In the blood, the parasites destroy the red blood cells, which carry vital oxygen to the tissues of the body. Some parasites stay in the liver and continue to multiply and periodically send more parasites into the bloodstream.

In most forms of malaria, this process results in repeated bouts of symptoms as parasites are periodically released into the bloodstream. Symptoms first appear in about eight to 30 days after a bite from an infected mosquito. Repeated bouts or attacks occur every two to three days. Symptoms are similar to those of the flu and typically include:

Attacks of malaria can occur for years if the disease is not diagnosed and treated. Eventually, the body’s immune system may develop a defense against malaria attacks, and they may become less severe in some people. However, treatment is needed to cure most forms of malaria.

Serious symptoms that might indicate a life-threatening condition

In some cases, malaria can progress into a life-threatening complication calledfalciparum malaria, in which a massive amount of Plasmodium parasites are released into the bloodstream at the same time.  Seek immediate medical care (call 911) if you, or someone you are with, have any of these symptoms:

  • Change in level of consciousness or alertness, such as passing out or unresponsiveness

  • Change in mental status or sudden behavior change, such as confusion, delirium, lethargy, hallucinations and delusions

  • Severe difficulty breathing and respiratory distress, such as labored breathing, wheezing, or not breathing

What causes malaria?

Malaria is caused by a tiny, microscopic parasite that belongs to the genus Plasmodium. P. vivax and P. falciparum are the two most common species that cause malaria. Plasmodium parasites are transmitted to humans by the bite of an Anopheles mosquito that is infected with the parasite. An Anopheles mosquito can only infect a person with malaria if it has already bitten a person with malaria.

Malaria is not a contagious disease that spreads directly from person to person, such as the cold or flu. However, an infected mother can transmit the malaria parasite to her baby before or during delivery. In addition, malaria can be transmitted by blood products (such as a blood transfusion), although this is a rare event.

After the Plasmodium parasites enter the human bloodstream, they travel to the liver and reproduce quickly. In most forms of malaria, some parasites stay in the liver to multiply, while others flow into the bloodstream. Once in the blood, the parasites destroy red blood cells, which carry vital oxygen to the tissues of the body.

The parasites continue to reproduce and periodically send more new parasites into the blood. This leads to repeated attacks of symptoms each time the malaria parasites are released into the blood.

What are the risk factors for malaria?

The risk factors for malaria include living or traveling to warm subtropical and tropical areas of the world where malaria is widespread including:

  • Africa

  • Caribbean

  • Central and South America

  • China

  • India

  • Middle East

  • South and Central Pacific

  • Southeast Asia

Reducing your risk of malaria

An important measure that reduces the risk of malaria is controlling mosquito populations in warm subtropical and tropical areas of the world where malaria is widespread. You may be able to lower your risk of exposure to mosquito bites by:

  • Draining areas and objects that can hold standing water and become a breeding ground for mosquitoes, such as old tires, puddles and bird baths

  • Taking antimalarial drugs as recommended for prevention of the disease

  • Wearing insect repellent that contains DEET, picaridin, or oil of lemon eucalyptus

  • Wearing protective clothing that covers the whole body

How is malaria treated?

Malaria is treated with antimalarial drugs. A combination of antimalarial drugs is often needed to completely cure malaria. Antimalarial drugs include:

  • Artemether-lumefantrine (Coartem)

  • Atovaquone-proguanil (Malarone)

  • Chloroquine

  • Mefloquine (Lariam)

  • Quinidine

  • Quinine

Severe cases of malaria and the life-threatening complications of severe anemia and falciparum malaria require hospitalization and intravenous administration of antimalarial drugs.

What are the possible complications of malaria?

In some cases, malaria can lead to a life-threatening complication called falciparum malaria. In falciparum malaria, all of the parasites that have reproduced in the liver are released into the bloodstream at the same time, which leads to an extremely severe attack of malaria. Symptoms and complications include:

  • Adverse effects of antimalaria treatment

  • Coma

  • Confusion

  • Kidney failure

  • Liver failure

  • Respiratory distress

  • Severe anemia (a decreased number of red blood cells), which occurs as large numbers of parasites destroy red blood cells. The remains of the destroyed red blood cells clump together and block blood vessels. This can result in brain or kidney damage.

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2021 Jan 18
THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
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