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

Malaria is a parasitic disease characterized by fever, chills, and anemia.

Causes, incidence, and risk factors

Malaria is caused by a parasite that is transmitted from one human to another by the bite of infected Anopheles mosquitoes. In humans, the parasites (called sporozoites) migrate to the liver where they mature and release another form, the merozoites. These enter the bloodstream and infect the red blood cells.

The parasites multiply inside the red blood cells, which then rupture within 48 to 72 hours, infecting more red blood cells. The first symptoms usually occur 10 days to 4 weeks after infection, though they can appear as early as 8 days or as long as a year later. Then the symptoms occur in cycles of 48 to 72 hours.

The majority of symptoms are caused by the massive release of merozoites into the bloodstream, the anemia resulting from the destruction of the red blood cells, and the problems caused by large amounts of free hemoglobin released into the circulation after red blood cells rupture.

Malaria can also be transmitted congenitally (from a mother to her unborn baby) 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 CDC estimates that there are 300 to 500 million cases of malaria each year, and more than one million people die. It presents the greatest disease hazard for travelers to warm climates.

In some areas of the world, mosquitoes that carry malaria have developed resistance to insecticides, while the parasites have developed resistance to antibiotics. This has led to difficulty in controlling both the rate of infection and spread of this disease.

Falciparum malaria, one of four different types, affects a greater proportion of the red blood cells than the other types and is much more serious. It can be fatal within a few hours of the first symptoms.


  • Sequential chills, fever, and sweating  
  • Headache  
  • Nausea and vomiting  
  • Muscle pain  
  • Anemia  
  • Stools, bloody  
  • Jaundice  
  • Convulsion  
  • Coma

Signs and tests

During a physical examination, the doctor may identify an enlarged liver and an enlarged spleen. Malaria blood smears taken at 6 to 12 hour intervals confirm the diagnosis.


Anti-malarial drugs can be prescribed to people traveling to areas where malaria is prevalent. It is important to see your health care provider well in advance of your departure, because treatment may begin 2 weeks before entering the area, and continue for 4 weeks after leaving the area. The types of anti-malarial medications prescribed will depend on the drug-resistance patterns in the areas to be visited.

According to the CDC, travelers going to South America, Africa, the Indian subcontinent, Asia, and the South Pacific should take one of the following drugs: mefloquine, doxycycline, chloroquine, hydroxychloroquine, or Malarone.

Malarone is a relatively new anti-malarial drug in the U.S. and is a combination of atovaquone and proguanil. It may be recommended over the other drugs mentioned, depending on your destination and the possibility of mefloquine resistance.

It is very important to know the countries and areas you will be visiting to obtain appropriate preventive support for malaria.


Malaria, especially Falciparum malaria, is a medical emergency requiring hospitalization. Chloroquine is the most frequently used anti-malarial medication, but quinidine or quinine, or the combination of pyrimethamine and sulfadoxine, are given for chloroquine-resistant infections.

Expectations (prognosis)

The outcome is expected to be good in most cases of malaria with treatment, but poor in Falciparum infection with complications.


  • Liver failure and kidney failure  
  • Destruction of blood cells (hemolytic anemia)  
  • Meningitis  
  • Rupture of the spleen and subsequent massive hemorrhage

Calling your health care provider
Call your health care provider if you develop fever and headache after visiting the tropics.


Most people living in malaria-prevalent areas have acquired some immunity to the disease. Visitors will not have immunity, and will need to take preventive medications. Even pregnant women should take preventive medications because the risk to the fetus from the medication is less than the risk of acquiring a congenital infection.

People on anti-malarial medications may still become infected. Avoid mosquito bites by wearing protective clothing over the arms and legs, using screens on windows, and using insect repellent.

Chloroquine has been the drug of choice for protection from malaria. With emerging resistance, it is now only indicated for use in areas where Plasmodium vivax, P. oval, and P. malariae are present. Falciparum malaria is becoming increasingly resistant to anti-malarial medications.

For travelers headed for areas Falciparum malaria is known to occur, the present drug of choice is mefloquine. Mefloquine has been approved by the FDA and is effective at preventing Falciparum malaria. Mefloquine can cause confusion and other mental side effects. Other drugs include Proguanil (available only in Africa), Fansidar (pyrimeth/sulfadoxine) and Malarone.

Travelers can call the CDC for information on types of malaria in a given geographical area, preventive drugs, and times of the season to avoid travel.

For information, call 1-800-311-3435 or go to the CDC web site and click on Travel Health.

Johns Hopkins patient information

Last revised: December 6, 2012
by Dave R. Roger, M.D.

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