Skip to main content
Update Location

My Location

Update your location to show providers, locations, and services closest to you.

Enter a zip code
Or
Select a campus/region

Definition

Malaria is a parasitic disease that involves high fevers, shaking chills, flu-like symptoms, and anemia.

Alternative Names

Quartan malaria; Falciparum malaria; Biduoterian fever; Blackwater fever; Tertian malaria; Plasmodium

Causes

Malaria is caused by a parasite. It is passed to humans by the bite of infected Anopheles mosquitoes. After infection, the parasites (called sporozoites) travel through the bloodstream to the liver. There, they mature and release another form of parasites, called merozoites. The parasites enter the bloodstream and infect red blood cells (RBCs).

The parasites multiply inside the red blood cells. The cells then break open within 48 to 72 hours and infect more red blood cells. The first symptoms usually occur 2 to 4 weeks after infection, though they can appear as early as 8 days or as long as a year after infection. The symptoms occur in cycles of 48 to 72 hours.

Most symptoms are caused by:

  • The release of merozoites into the bloodstream
  • Anemia resulting from the destruction of the red blood cells
  • Large amounts of free hemoglobin being released into circulation after red blood cells break open, which can damage other organs such as the kidneys

Malaria can also be transmitted from a mother to her unborn baby (congenitally) and by blood transfusions. Malaria can be carried by mosquitoes in temperate climates, but the parasite disappears over the winter.

The disease is a major health problem in much of the tropics and subtropics. The Centers for Disease Control and Prevention reported that in 2020 there were about 241 million cases of malaria. About 627,000 people died of it. Malaria is a major disease hazard for travelers to warm climates.

In some areas of the world, mosquitoes that carry malaria have developed resistance to insecticides. In addition, the parasites have developed resistance to some antibiotics. These conditions have made it hard to control both the rate of infection and spread of this disease.

Symptoms

Symptoms include:

Exams and Tests

During a physical examination, the health care provider may find an enlarged liver or enlarged spleen.

Tests that are done include:

  • Rapid diagnostic tests, which are becoming more common because they are easier to use and require less training by laboratory technicians
  • Malaria blood smears taken at 6 to 12 hour intervals to confirm the diagnosis
  • A complete blood count (CBC) will identify anemia if it is present

Treatment

Malaria, especially falciparum malaria, is a medical emergency that requires a hospital stay. Chloroquine is often used as an anti-malarial medicine. But chloroquine-resistant infections are common in some parts of the world.

Possible treatments for chloroquine-resistant infections include:

  • Artemisinin derivative combinations, including artemether and lumefantrine
  • Atovaquone-proguanil
  • Quinine-based regimen, in combination with doxycycline or clindamycin
  • Mefloquine, in combination with artesunate or doxycycline

The choice of medicine depends, in part, on where you got the infection.

Medical care, including fluids through a vein (IV) and other medicines and breathing (respiratory) support may be needed.

Outlook (Prognosis)

Outcome is expected to be good in most cases of malaria with treatment, but poor in falciparum infection with complications.

Possible Complications

Health problems that may result from malaria include:

When to Contact a Medical Professional

Contact your health care provider if you develop fever and headache after visiting any foreign country.

Prevention

Most people who live in areas where malaria is common have developed some immunity to the disease. Visitors will not have immunity and should take preventive medicines.

It is important to see your provider well before your trip. This is because treatment may need to begin as long as 2 weeks before travel to the area, and continue for a month after you leave the area. Most travelers from the United States who contract malaria fail to take the right precautions.

The types of anti-malarial medicines prescribed depend on the area you visit. Travelers to South America, Africa, the Indian subcontinent, Asia, and the South Pacific should take one of the following medicines:

  • Mefloquine
  • Doxycycline
  • Chloroquine
  • Hydroxychloroquine
  • Atovaquone-proguanil

Even pregnant women should consider taking preventive medicines because the risk to the fetus from the medicine is less than the risk of catching this infection.

Chloroquine has been the medicine of choice for protecting against malaria. But because of resistance, it is now only suggested for use in areas where Plasmodium vivax, P oval, and P malariae are present.

Falciparum malaria is becoming increasingly resistant to anti-malarial medicines. Recommended medicines include mefloquine, atovaquone/proguanil (Malarone), and doxycycline.

Prevent mosquito bites by:

  • Wearing protective clothing over your arms and legs
  • Using mosquito netting while sleeping
  • Using insect repellent

For information on malaria and preventive medicines, visit the CDC website: www.cdc.gov/malaria/travelers/index.html.

Gallery

Malaria, microscopic view of cellular parasites
Malaria is a disease caused by parasites that are carried by mosquitoes. Once in the bloodstream, the parasite inhabits the red blood cell (RBC). This picture shows purple-stained malaria parasites inside red blood cells.
Mosquito, adult feeding on the skin
There are many different species of mosquito, which can carry some of the world's most common and significant infectious diseases, including West Nile, Malaria, yellow fever, viral encephalitis, and dengue fever. (Image courtesy of the Centers for Disease Control and Prevention.)
Mosquito, adult feeding on the skin
There are many different species of mosquito, which can carry some of the world's most common and significant infectious diseases, including West Nile, Malaria, yellow fever, viral encephalitis, and dengue fever. (Image courtesy of the Centers for Disease Control and Prevention.)
Mosquito, adult feeding on the skin
There are many different species of mosquito, which can carry some of the world's most common and significant infectious diseases, including West Nile, Malaria, yellow fever, viral encephalitis, and dengue fever. (Image courtesy of the Centers for Disease Control and Prevention.)
Mosquito, adult feeding on the skin
There are many different species of mosquito, which can carry some of the world's most common and significant infectious diseases, including West Nile, Malaria, yellow fever, viral encephalitis, and dengue fever. (Image courtesy of the Centers for Disease Control and Prevention.)
Red blood cells, sickle cell
Sickle cell anemia is an inherited blood disease in which the red blood cells produce abnormal pigment (hemoglobin). The abnormal hemoglobin causes deformity of the red blood cells into crescent or sickle-shapes, as seen in this photomicrograph.
Red blood cells, sickle cell
Sickle cell anemia is an inherited blood disease in which the red blood cells produce abnormal pigment (hemoglobin). The abnormal hemoglobin causes deformity of the red blood cells into crescent or sickle-shapes, as seen in this photomicrograph.
Infectious diseases and travelers
Different areas of the world have different diseases and different prevalence rates of diseases. Travelers going to foreign countries may encounter diseases to which they have no natural immunity and should take any possible precautions.
Digestive system organs
The digestive system organs in the abdominal cavity include the liver, gallbladder, stomach, small intestine and large intestine.

References

Ansong D, Seydel KB, Taylor TE. Malaria. In: Ryan ET, Hill DR, Solomon T, Aronson NE, Endy TP, eds. Hunter's Tropical Medicine and Emerging Infectious Diseases. 10th ed. Philadelphia, PA: Elsevier; 2020:chap 101.

Fairhurst RM, Wellems TE. Malaria (Plasmodium species). In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 9th ed. Philadelphia, PA: Elsevier; 2020:chap 274.

Freedman DO. Protection of travelers. In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 9th ed. Philadelphia, PA: Elsevier; 2020:chap 318.

Last reviewed May 19, 2023 by Jatin M. Vyas, MD, PhD, Associate Professor in Medicine, Harvard Medical School; Associate in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital, Boston, MA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team..

Related specialties

Our locations

Our experts

News and Patient Stories: Malaria

More Malaria stories

Latest podcast episodes

U.S. sees record number of malaria cases

When the national Centers for Disease Control and Prevention was founded in 1946, one of its goals was to eradicate malaria in the United States. Thanks to previous efforts and a partnership with...

The buzz about malaria

Most people view mosquitoes as dirty, harmful disease carriers. But these blood-sucking...

Listen to more Health in a Heartbeat episodes