Malaria

Topic Overview

What is malaria?

Malaria is a serious disease that causes a high fever and chills. You can get it from a bite by an infected mosquito. Malaria is rare in the United States. It is most often found in Africa, Southern Asia, Central America, and South America.

What causes malaria?

Malaria is caused by a bite from a mosquito infected with parasites. In very rare cases, people can get malaria if they come into contact with infected blood. A developing fetus may get the disease from its mother. You cannot get malaria just by being near a person who has the disease.

What are the symptoms?

Most malaria infections cause symptoms like the flu, such as a high fever, chills, and muscle pain. Symptoms tend to come and go in cycles. Some types of malaria may cause more serious problems, such as damage to the heart, lungs, kidneys, or brain. These types can be deadly.

How is malaria diagnosed?

Your doctor will order a blood test to check for the malaria parasite in your blood.

How is it treated?

Medicines usually can treat the illness. But some malaria parasites may survive because they are in your liver or they are resistant to the medicine.

Get medical help right away if you have been in an area where malaria is present, were exposed to mosquitoes, and get symptoms that are like the flu. These include a high fever, chills, and muscle pain.

How is malaria prevented?

You may be able to prevent malaria by taking medicine before, during, and after travel to an area where malaria is present. But using medicine to prevent malaria doesn't always work. This is partly due to the parasites being resistant to some medicines in some parts of the world.

Frequently Asked Questions

Learning about malaria:

Being diagnosed:

Getting treatment:

Ongoing concerns:

Cause

A bite from a parasite-infected mosquito causes malaria. There are five species of Plasmodium (P.) parasites that infect people.

Infection with P. falciparum

  • P. falciparum is found mostly in the tropics and subtropics (near the equator).
  • Infection with P. falciparum can lead to life-threatening complications after the first few days.
  • P. falciparum is often resistant to a popular antimalarial medicine (chloroquine) and needs treatment with other medicines.

Infection with P. vivax, P. malariae, P. ovale, or P. knowlesi

  • P. vivax and P. malariae occur all over the tropical regions of the world. P. ovale is found in western Africa, and P. knowlesi is found in Southeast Asia.
  • Infection with P. vivax, P. malariae, or P. ovale is usually not life-threatening, and a person may recover in a month without treatment. But infection with P. knowlesi may be fatal.
  • P. vivax, P. malariae, P. ovale, and P. knowlesi are generally not as drug-resistant as P. falciparum.
  • P. vivax, P. ovale, and P. knowlesi may stay in the liver, requiring further treatment with medicine to prevent relapses.

How the disease spreads

Malaria is spread when an infected Anopheles mosquito bites a person. This is the only type of mosquito that can spread malaria. The mosquito becomes infected by biting an infected person and drawing blood that contains the parasite. When that mosquito bites another person, that person becomes infected.

In the United States, people who develop malaria almost always got infected while traveling in parts of the world where malaria is common. For more information, see the topic Travel Health.

Symptoms

When symptoms appear

Malaria can begin with flu-like symptoms. In the early stages, infection from P. falciparum is similar to infection from P. vivax, P. malariae, and P. ovale. You may have no symptoms or symptoms that are less severe if you are partially immune to malaria.

The time from the initial malaria infection until symptoms appear (incubation period) typically ranges from:2

  • 9 to 14 days for Plasmodium (P.) falciparum.
  • 12 to 18 days for P. vivax and P. ovale.
  • 18 to 40 days for P. malariae.
  • 11 to 12 days for P. knowlesi.

Symptoms can appear in 7 days. And the time between exposure and signs of illness may sometimes be as long as 8 to 10 months with P. vivax and P. ovale.

The incubation period may be longer if you are taking medicine to prevent infection (chemoprophylaxis) or because you have some immunity due to previous infections.

Variation in symptoms

In regions where malaria is present, people who get infected many times may have the disease but have few or no symptoms.3 Also, how bad malaria symptoms are can vary depending on your general health, what kind of malaria parasite you have, and whether you still have your spleen.

Common symptoms of malaria

In the early stages, malaria symptoms are sometimes similar to those of many other infections caused by bacteria, viruses, or parasites. Symptoms may include:

  • Fever.
  • Chills.
  • Headache.
  • Sweats.
  • Fatigue.
  • Nausea and vomiting.

Symptoms may appear in cycles. The time between episodes of fever and other symptoms varies with the specific parasite you are infected with. Episodes of symptoms may occur:

  • Every 48 hours if you are infected with P. vivax or P. ovale.
  • Every 72 hours if you are infected with P. malariae.

P. falciparum does not usually cause a regular, cyclic fever.

The cyclic pattern of malaria symptoms is due to the life cycle of malaria parasites as they develop, reproduce, and are released from the red blood cells and liver cells in the human body. This cycle of symptoms is also one of the major signs that you are infected with malaria.

Other common symptoms of malaria

Other common symptoms of malaria include:

  • Dry (nonproductive) cough.
  • Muscle or back pain or both.
  • Enlarged spleen.

In rare cases, malaria can lead to impaired function of the brain or spinal cord, seizures, or loss of consciousness.

Infection with the P. falciparum parasite is usually more serious and may become life-threatening.

There are other conditions with symptoms similar to a malaria infection. It is important that you see your doctor to find out the cause of your symptoms.

What Happens

When you're bitten by a malaria-infected mosquito, the parasites that cause malaria are released into your blood and infect your liver cells. The parasite reproduces in the liver cells, which then burst open. This allows thousands of new parasites to enter the bloodstream and infect red blood cells. The parasites reproduce again in the blood cells, kill the blood cells, and then move to other uninfected blood cells.

After the early stages, life-threatening complications may develop rapidly with P. falciparum and P. knowlesi. If the infected person is not treated, serious complications or death can occur.

But you may recover in a week to a month (or longer) after being infected with P. vivax, P. malariae, or P. ovale, even without treatment.

Malaria can be a very serious disease for a pregnant woman and her developing fetus, for people without a spleen, and for young children. Medicine choices are limited for a pregnant woman or a child. Infection with P. falciparum can lead to death for a pregnant woman and her fetus. For these reasons, a pregnant woman should not travel to an area where she could get P. falciparum malaria. Visit the CDC website (www.cdc.gov/malaria/travelers/index.html) to find out whether malaria is a problem in the country where you will be traveling.

Malaria recurrences

Malaria caused by P. falciparum may come back (recur) at irregular intervals for up to 2 years if treatment is not complete.

Malaria caused by P. vivax and P. ovale may recur at irregular intervals for up to 3 to 4 years, but medicine can prevent relapses.

P. malariae can remain in the blood of an infected person for more than 30 years, usually without causing any symptoms.

What Increases Your Risk

Risk factors (things that increase your risk) for getting malaria include:

  • Living or traveling in a country or region where malaria is present.
  • Traveling in an area where malaria is common and:
    • Not taking medicine to prevent malaria before, during, and after travel, or failing to take the medicine correctly.
    • Being outdoors, especially in rural areas, between dusk and dawn (nighttime), when the mosquitoes that transmit malaria are most active.
    • Not taking steps to protect yourself from mosquito bites.

Your risk of getting malaria depends on your age, history of exposure to malaria, and whether you are pregnant. Most adults who have lived in areas where malaria is present have developed partial immunity to malaria because of previous infections and so almost never develop severe disease. But young children who live in these areas and travelers to these areas are especially at risk for malaria because they have not developed this immunity.

Pregnant women are more likely than nonpregnant women to get severe malaria, because the immune system is suppressed during pregnancy.

Also, pregnant women, young children, older adults, and people with other health problems are more likely to have serious complications if they get malaria.

You can take measures to reduce the risk of malaria if you live in areas where the disease is present or if you are traveling in these areas.

Malaria is more severe in people who have had their spleen removed (splenectomy).

When To Call a Doctor

Call a doctor immediately if you have been in an area where malaria is present, were exposed to mosquitoes, and develop flu-like symptoms (such as fever, chills, headache, and nausea).

Watchful waiting

Watchful waiting is a wait-and-see approach. If you get better on your own, you won't need treatment. If you get worse, you and your doctor will decide what to do next.

Do not wait to call a doctor if you think you have malaria. Call a doctor immediately.

For people who live for many years in countries where malaria is common and have some immunity to malaria, watchful waiting is okay for mild malaria symptoms. Flu-like symptoms may also be caused by many other diseases or health conditions. Watchful waiting is not appropriate for most travelers. If you have a question about your symptoms, call your doctor.

Who to see

Health professionals who can check out symptoms that may be caused by malaria include:

In the United States, call the Centers for Disease Control and Prevention (CDC) toll-free at 1-800-232-4636 (1-800-CDC-INFO) or visit the CDC's malaria website (www.cdc.gov/malaria) to receive the most current information about malaria and appropriate travel precautions. Your doctor or local health department may also have this information.

To prepare for your appointment, see the topic Making the Most of Your Appointment.

Exams and Tests

Doctors use thick and thin blood smears to find out whether malaria-causing parasites are in your blood. These tests should be done if you have been in a region where malaria is present, you were exposed to mosquitoes, and you have flu-like symptoms.

  • A blood smear is prepared from a blood sample.
  • If the first blood smear does not show the presence of malaria parasites but your doctor suspects malaria, you should have a repeat test every 8 to 12 hours for 36 hours.
  • During treatment, doctors use blood smears to see whether the number of malaria parasites in the blood is decreasing.

A blood test that can diagnose malaria rapidly also is available. If this rapid test indicates a person has malaria, the results are usually confirmed with a blood smear.

Other tests

Other useful tests that may be done include:

  • Liver function tests, to check for liver damage.
  • Complete blood count (CBC), to check for anemia or evidence of other possible infections. Anemia sometimes develops in people with malaria, because the parasites damage red blood cells.
  • A blood glucose test, to measure the amount of a type of sugar, called glucose, in your blood.

Other tests being developed to diagnose malaria include genetic tests or other blood tests that highlight parasites by using special stains. These experimental tests are not as easy to do and are not as frequently used as blood smears.

In the United States, malaria is an infectious disease that must be reported to the local or state health department.

Treatment Overview

Medicine can prevent malaria and is needed to treat the disease. Several things influence the choice of medicine, including:

  • Whether the medicine is being used to prevent or to treat malaria.
  • Your condition (such as your age or whether you are pregnant).
  • How sick you are from malaria.
  • Geographic location where you were exposed to malaria.
  • Whether the malaria parasite may be resistant to certain medicines.
  • Side effects of the medicine.

Malaria is rare in the United States. But it is widespread in other parts of the world. Find out about the risk for malaria before you travel internationally. The most accurate information about malaria risk and medicine resistance in specific countries is from the Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO).

If you have malaria, medicine choice is based on:

  • The specific parasite causing the infection.
  • How bad the infection is.
  • Your condition (such as age, pregnancy, allergies, or health problems).
  • Medicine resistance of the parasite found in the geographic area where you were infected.

If you have been in an area where malaria occurs, were exposed to mosquitoes, and have flu-like symptoms, but tests do not show the malaria parasite in your blood, the tests should be repeated 3 or 4 times to confirm that you do not have a malaria infection. During treatment, tests are repeated to follow the course of the infection and to check whether the number of parasites is decreasing.

Your age and health condition are important factors in selecting a medicine to prevent or treat malaria. Pregnant women, children, people who are very old, people who have other health problems, and those who did not take medicine to prevent malaria infection require special consideration.

Prevention

Prevention of malaria involves protecting yourself against mosquito bites and taking antimalarial medicines. But public health officials strongly recommend that young children and pregnant women avoid traveling to areas where malaria is common.

The most current information about malaria is available from the Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO). If you are planning international travel, you can learn about the risk of malaria in that geographic area and the medicines recommended to prevent infection by contacting:

  • The CDC at its toll-free phone number (1-800-232-4636) or website (www.cdc.gov/malaria/travelers/index.html).
  • Your doctor or local health department.

Prevent mosquito bites

To prevent mosquito bites, follow these guidelines:

  • Stay inside when it is dark outside, preferably in a screened or air-conditioned room.
  • Wear protective clothing (long pants and long-sleeved shirts).
  • Use insect repellent with DEET (N,N diethylmetatoluamide). The repellent is available in varying strengths up to 100%. In young children, use a preparation containing less than 24% strength, because too much of the chemical can be absorbed through the skin.
  • Use bed nets (mosquito netting) sprayed with or soaked in an insecticide such as permethrin or deltamethrin. But make sure that these insecticides still work against the mosquitoes where you are. In some areas, mosquitoes have become resistant to permethrin and deltamethrin. So the bed nets do not offer much protection.4
  • Use flying-insect spray indoors around sleeping areas.
  • Avoid areas where malaria and mosquitoes are present if you are at higher risk (for example, if you are pregnant, very young, or very old).

Other steps that may be helpful in reducing the risk of malaria include using air conditioning and electric fans, wearing protective clothing, using aerosol insecticides in your house, and taking certain antimalarial medicines.5

Medicines to prevent malaria

The selection of medicines to prevent malaria depends on the geographic region where you may be exposed to malaria and your health condition (such as being pregnant, being elderly or young, being sick, or having immunity or resistance to malaria, or having allergies or sensitivity to the medicine).

If you are going to a location where malaria is present, it is very important to take preventive medicines and to follow the correct schedule for taking them. The majority of people who become infected with malaria do not take preventive malaria medicines or do not follow the correct dosing schedule.

  • Medicine to prevent malaria is most effective if you take the recommended dosage exactly as prescribed and for the length of time required.
  • If you are to take the medicine once a week, take it on the same day of the week each week.
  • Upon returning from an area where malaria is present, continue the medicine for the recommended length of time to ensure that all parasites have been eliminated from your body. You will need to take the medicine for 1 to 4 weeks after returning.

Malaria vaccines

Scientists are studying malaria vaccines to see whether the vaccines are effectively preventing malaria infection. But no vaccine has been approved to prevent malaria.1, 5 Work continues on improving vaccines for preventing malaria.

Home Treatment

If you plan to travel in remote areas where malaria is present, it is very important to take preventive medicines and to follow the correct schedule for taking them. The majority of people who become infected with malaria did not take preventive malaria medicines or did not follow the correct dosing schedule.

If you are going to areas where there is no medical care available, you can get medicine before you leave and carry it with you while you travel. Your doctor will give you instructions on how to use the medicine if you should develop malaria symptoms. This is a temporary measure until you can get medical care. Seek medical care as soon as possible (ideally within 24 hours).

The most current information about the prevention and treatment of malaria is from the Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO). Contact the CDC at its toll-free phone number (1-800-232-4636) or website (www.cdc.gov/malaria). The WHO website is www.who.int/malaria.

Medications

You can take medicines called antimalarials to prevent and treat malaria. Malaria is a very serious disease, and its presence in many regions of the world is well known. So if you are traveling to an area where malaria is present, it is important to reduce the risk of infection by taking medicine before you travel, while you are in the area, and after you return home. Which medicine you take is based on:

  • The country or areas in which you will be traveling.
  • The resistance of malaria parasites to certain medicines in the area where you will be traveling.
  • Your health condition (for example, whether you are pregnant, elderly or young, sick, or have immunity or resistance to malaria).

It is important to know which species of parasite is present, because serious complications may develop rapidly in a person who is infected with Plasmodium (P.) falciparum. Drug treatment is based on:

  • The species of parasite. If you are infected with P. falciparum, life-threatening complications can develop rapidly. Infection caused by one of the other four species of malaria parasite is rarely life-threatening.
  • The density of parasites. If the percentage of red blood cells infected (parasite density) is over 5%, treatment may include medicines given directly into a vein (intravenously, or IV) rather than medicine taken by mouth.
  • Your health condition. You are at higher risk for having complications if you are pregnant, elderly, very young, or have a weak immune system. Different medicines may be prescribed for people in these groups.
  • Drug resistance in the geographic area where the infection occurred. For instance, in many areas P. falciparum is resistant to the drug chloroquine.

During malaria treatment, your doctor may do daily blood smears to follow the course of the infection. Most medicines for malaria are ones you take by mouth. But you might get intravenous (IV) medicines if there are complications or your condition gets worse. If there are no complications, your fever will clear in 36 to 48 hours. And most parasites will disappear from your blood within 2 or 3 days.

The medicines used may change as malaria parasites develop resistance and as new medicines are developed.

Medicine choices

There are several medicines for preventing and treating malaria.

Medicines to prevent malaria

A doctor or local health department can consult the CDC for specific treatment guidelines for your travel destination. Standard medicines for preventing malaria include:

  • Chloroquine. You can take chloroquine to prevent P. falciparum and P. vivax infections in areas where medicine resistance to chloroquine has not been confirmed.
  • Doxycycline. You can take doxycycline if you cannot take mefloquine. Women who are pregnant and children younger than age 9 should not take this medicine.
  • Malarone. Malarone is a combination of two antimalarial medicines (atovaquone and proguanil). Malarone is taken to prevent malaria caused by P. falciparum.
  • Mefloquine. You can take mefloquine to prevent malaria infections unless the malaria parasite in the area you're visiting is resistant to mefloquine. Do not take mefloquine if you have a history of active or recent depression or other mental illness, seizures, or some types of heart-rhythm problems.
  • Primaquine. You take primaquine to prevent relapses of P. vivax and P. ovale malaria. You should be tested for glucose-6-phosphate dehydrogenase deficiency before taking primaquine.
Medicines to treat infections
  • Chloroquine is the most effective medicine for treating a malaria infection caused by P. ovale or P. malariae parasites. To prevent relapses of infections caused by these two parasites, continue taking chloroquine after you leave the area where these parasites are present. Chloroquine is also used to treat P. falciparum and P. vivax infections in areas where resistance to chloroquine has not been confirmed.
  • Coartem is a combination of the two medicines artemether and lumefantrine. It is used to treat malaria caused by P. falciparum.
Medicines to treat chloroquine-resistant infections

When a malaria infection is caused by resistant strains of P. falciparum or P. vivax, treatment may be more difficult. When treatment with chloroquine does not work, you must take other medicines. These medicines may include:

  • Coartem, which is a combination of the two medicines artemether and lumefantrine. It is used to treat malaria caused by chloroquine-resistant P. falciparum.
  • Doxycycline, for infections caused by P. falciparum and P. vivax in Thailand and Kenya.
  • Malarone, which is a combination of two antimalarial medicines (atovaquone and proguanil). Malarone is taken to treat malaria caused by chloroquine-resistant P. falciparum.
  • Quinine plus an antibiotic such as clindamycin, doxycycline, or tetracycline for most P. falciparum infections. It should not be used in Southeast Asia, where quinine effectiveness is declining. It is only somewhat effective in Thailand.

You can get antimalarials intravenously (IV) if you are unable to take pills. IV delivery is also used for severe malaria. In the United States, quinidine is the medicine typically used in these situations.

Antimalarials to prevent recurrences

Some people have recurring flu-like symptoms for years after the initial malaria infection. Relapses from infection of P. vivax or P. ovale are the most common and can be prevented by taking primaquine.

What to think about

  • Children who weigh less than 33 lb (15 kg) should not visit an area that has a risk of chloroquine-resistant malaria.
  • How effective medicines are in preventing and treating malaria depends on the medicine resistance of the parasites in the geographic location where the malaria infection occurs.
  • If you are going to a location where malaria is present, it is very important to take preventive medicines and to follow the correct schedule for taking them. The majority of people who become infected with malaria did not take preventive malaria medicines or did not follow the correct dosing schedule.
  • Pregnant women should discuss medicine options with their doctors.

Other Treatment

Exchange blood transfusions

Exchange blood transfusions may be considered for treating severe cases of malaria if:6

  • The percentage of blood cells infected with the parasite (parasite density) is greater than 10%.
  • You have altered mental capacity (severe confusion) due to the malaria infection.
  • You have lung or kidney complications.

Exchange blood transfusion is the quickest way to remove parasites. This procedure involves withdrawing blood from you at the same time that donor blood is being injected. During this exchange, the amount of blood in your body stays constant. Quinine is given by needle into a vein (intravenously) at the same time as the blood transfusion. Parasite density is checked every 12 hours until it is less than 1%.6

Other Places To Get Help

Organization

Centers for Disease Control and Prevention (CDC) Malaria Page
Web Address: www.cdc.gov/malaria

References

Citations

  1. Suh KN, et al. (2004). Malaria. Canadian Medical Association Journal, 170(11): 1693–1702.
  2. American Public Health Association (2008). Malaria. In DL Heymann, ed., Control of Communicable Diseases Manual, 19th ed., pp. 373–393. Washington, DC: American Public Health Association.
  3. Fairhurst RM, Wellems TE (2010). Plasmodium species (malaria). In GL Mandell et al., eds., Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases, 7th ed., vol. 2, pp. 3437–3462. Philadelphia: Churchill Livingstone Elsevier.
  4. Asidi A, et al. (2012). Loss of household protection from use of insecticide-treated nets against pyrethroid-resistant mosquitoes, Benin. Emerging Infectious Diseases, 18(7): 1101–1106. Also available online: http://wwwnc.cdc.gov/eid/article/18/7/12-0218_article.htm.
  5. Croft AM (2010). Malaria: Prevention in travellers, search date November 2009. Online version of Clinical Evidence (7).
  6. Centers for Disease Control and Prevention (2011). Treatment of malaria (guidelines for clinicians). Available online: http://www.cdc.gov/malaria/resources/pdf/clinicalguidance.pdf.

Other Works Consulted

  • Day N (2008). Malaria. In M Eddleston et al., eds., Oxford Handbook of Tropical Medicine, 3rd ed., pp. 31–65. Oxford: Oxford University Press.
  • Freedman DO (2008). Malaria prevention in short-term travelers. New England Journal of Medicine, 359(6): 603–612.

Credits

By Healthwise Staff
E. Gregory Thompson, MD - Internal Medicine
W. David Colby IV, MSc, MD, FRCPC - Infectious Disease
Last Revised August 5, 2013

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