Malaria: Causes, Symptoms, and Treatment

Medically Reviewed by Brunilda Nazario, MD on June 29, 2023
Written by WebMD Editorial Contributors
9 min read

Malaria is a serious and sometimes life-threatening disease you can get from a mosquito bite.  

Malaria is not common in the U.S. But you can get it when you travel to other parts of the world. There are about 2,000 cases a year in the U.S. They mostly come from immigrants and travelers returning from countries where malaria is more common. There have been cases of people getting malaria within the U.S., but that's rare. Countries with more malaria outbreaks have climates that are hot enough for the parasites that cause the disease and the mosquitoes that carry them to thrive. 

There are ways to try to prevent malaria. Before you travel, check the CDC’s website to see whether your destination is a hotspot for malaria. You may have to take pills before, during, and after your trip to lower your chances of getting it.

Though death from malaria can usually be prevented -- especially in the U.S. where medicines are more available -- it kills about 620,000 people a year, many of them children in Africa.

 

Malaria is caused by plasmodium parasites, which are carried by a certain type of mosquito called anopheles. 

Only female mosquitoes spread the malaria parasites. 

 

 

When a mosquito bites a person who has malaria, it drinks the person’s blood, which contains the parasites. When the mosquito bites another person, it injects the parasites into that person. That’s how the disease spreads.

Once the parasites enter your body, they travel to your liver, where they multiply. They get into your red blood cells, lay their eggs, and multiply until the red blood cells burst. This releases more parasites into your bloodstream. As they attack more of your healthy red blood cells, this infection can make you very sick.

About half of the world's population is at risk for getting malaria.

You have a higher risk for getting malaria depending on where you live or travel. Malaria is most common in warm-weather climates. It’s often found in:

  • Africa
  • South and Southeast Asia
  • The Middle East
  • Central and South America 
  • Australia, New Zealand, and other islands in the western Pacific

Some people have a higher risk of getting a serious case of malaria. These include:

  • Children and babies
  • People who have HIV or AIDS
  • Pregnant people
  • Travelers who live in areas without malaria

If you live in a place with high malaria rates, you may become partially immune to it. This means your symptoms may not be as serious if you get it. But your immunity can decrease if you move somewhere that exposes you less to the parasite. 

Malaria isn’t contagious, meaning it can’t be spread from person to person. 

Though rare, it can spread in these ways:

  • From a pregnant mother to their unborn baby
  • Sharing needles
  • Blood transfusions
  • Organ transplant

There are five species of plasmodium parasites that affect humans. Two of them are considered the most dangerous:

P. falciparum. This is the most common malaria parasite in Africa. It causes the most malaria-related deaths in the world. P. falciparum multiplies quickly, causing serious blood loss and clogged blood vessels.

P. vivax. This is the malaria parasite most commonly found outside of sub-Saharan Africa, especially in Asia and Latin America. This species can lie dormant, then rise up to infect your blood months or years after the mosquito bite.

The other types of malaria are:

  • P. malariae
  • P. ovale
  • P. knowlesi

Symptoms for malaria usually start about 10-15 days after getting bitten by an infected mosquito. Symptoms of malaria can include:

Malaria symptoms can be similar to cold or flu symptoms, so it might be hard to tell what you have at first. Malaria symptoms don’t always show up within 2 weeks, especially if it’s a P. vivax infection.

Malaria can get serious quickly, so it’s important to get medical care as soon as possible. Early treatment can better keep it from getting serious or being life-threatening.

Because malaria isn't common in the U.S., medical professionals must be aware that people here can get it. Sometimes a fever, for example, may not be a  red flag. But if you have other symptoms like having a hard time breathing or you're in a coma, doctors may suspect it.

If you think you may have malaria while you're traveling to an area where it's common, get medical care right away. Give the doctor your medical history. You can also ask your doctor about traveling with a full set of medication on you -- just in case you need it while you're far from home.

If you're returned home and think you have malaria, you should still get medical help even if your symptoms come up many weeks, months, or a year after your travel.

 

Your doctor will ask you about your medical history and any recent travel and do a physical exam.

You’ll also get a blood test, which can tell your doctor:

  • If the parasite is in your blood
  • If certain medications will work against the parasite
  • If your body has ever made antibodies to fight off malaria 

Types of blood tests for malaria include:

Thick and thin blood smears. These are the most common and accurate malaria tests. A lab technician, doctor, or nurse will take some of your blood and send it to a lab to be stained to make any parasites show clearly. The technician spreads it on a glass slide and looks at it with a microscope. A thin blood smear, also called a blood film, is one drop of blood spread across most of the slide. A thick smear drops the blood on a small area. A normal test does two of each.

The number of malaria parasites in your blood can change each day. So your test might say you don’t have malaria even if you do. For that reason, you may need your blood drawn several times over 2 or 3 days for the best results.

Rapid diagnostic test. Also called RDT or antigen testing, this is a quick option when blood draws and smears aren't available. Blood taken from a prick on your finger is put on a test strip that changes color to show whether you have malaria or not.

This test usually can't tell which of the four common species of malaria parasites caused your infection. It also can’t tell whether the infection is minor or major. Your doctor should follow up all results with blood smears.

Molecular test. Also known as polymerase chain reaction test, it can identify the type of parasite, which helps your doctor decide which drugs to prescribe. This test is a good choice if your blood has low number of parasites or if the results of your blood smear are vague.

Antibody test. Doctors use this to find out if you've had malaria before. It looks for antibodies that show up in the blood after an infection.

Drug resistance test. Some malaria parasites are resistant to drugs. But doctors can test your blood to see if certain drugs will work.

Other blood tests. You may also have blood taken for a blood count and chemistry panel. This can tell your doctor how serious your infection is and if it's causing other problems, like anemia or kidney failure.

The treatment your doctor recommends will depend on things like:

  • The type of parasite you have
  • How bad your symptoms are
  • The geographic area where you got infected
  • Your age 
  • Whether you’re pregnant

Some medications doctors use to treat malaria include:

  • Chloroquine or hydroxychloroquine. Your doctor may recommend one of these drugs if your symptoms aren’t serious and you’re in an area where the parasite hasn’t become resistant to chloroquine. 
  • Artemisinin-based combination therapy (ACT). This combines two medicines that work in different ways. They’re used to treat milder cases of malaria or as part of a treatment plan for more serious cases. 
  • Atovaquone-proguanil, artemether-lumefantrine. These combinations are other options in areas where the parasite has become resistant to chloroquine. They also can be given to children.
  • Mefloquine. This medication is another option if chloroquine can’t be used, but it’s been linked to rare but serious side effects related to your brain and is only used as a last resort.
  • Artesunate. If your symptoms are serious, your doctor may give you this drug for the first 24 hours. It's given intravenously, which means it's injected through a needle into your vein. After you get it, they may follow up with with 3 days of artemisinin-based combination therapy. 

Some parasites that cause malaria have become resistant to almost all the medicines used to treat the illness, so researchers are always looking for new drugs.

Serious health problems that can come with malaria include:

  • Coma
  • Cerebral malaria (brain damage caused by swelling)
  • Pulmonary edema
  • Liver, kidney, and spleen failure
  • Anemia (when you lose too many red blood cells)
  • Very low blood sugar

You can get malaria again after you've had it one time. Some types of the parasite cause a milder form of illness that can last for a long time and come back. 

 

If you're traveling to an area where malaria is common, there are a few ways to protect yourself from mosquito bites that may contain the malaria parasite.

  • Protect your skin with clothing. Cover your skin with clothing such as pants, long-sleeved shirts, and hats. Tuck in any edges where skin may be exposed. You can also spray permethrin on clothing for added protection.
  • Wear insect repellent. Put repellent on any skin not covered with clothing, but not under clothing. Apply products with DEET, picaridin, IR3535, oil of lemon eucalyptus (OLE), para-menthane-3,8-diol (PMD), or 2-undecanone. But don't use oil of lemon eucalyptus (OLE) or p-menthane-3,8-diol (PMD) on children under age 3. The U.S. Environmental Protection Agency has a search tool to help you find the right repellent.
  • Layer your sun protection. If you're wearing sunscreen, put that on first. Then put on a bug repellent.
  • Bring a bed net. Netting can go over your bed to protect you from bites when you sleep. It can also be sprayed with an insecticide like permethrin. 
  • Take a preventive medicine. Ask your doctor about different medicines that may help. They may prescribe one depending on where you are headed, or if you're on any other drugs that may interact with the preventive medicine. You may have to take the drug before you go, while you're there, and after you get home. Be sure to purchase it in your home country to avoid fake products. Write down the drug's brand and generic names, and keep that on you. Keep the drug in its original package.
  • Avoid travel in some cases. If you're pregnant and you don't have to travel to an area affected by malaria, try to avoid making the trip. If you have to take the trip, take preventive medicine.
  • Use the CDC's tools. The CDC has a lot of resources online that can tell you what you should do if you're traveling to a specific country, what types of parasites are there, and any medicines you can take to try to stop malaria. 
  • Travel smart. Check into the Department of State’s Smart Traveler Enrollment Program (STEP), which can help the U.S. government track you if you have any medical issues while traveling. They also have a list of list of travel medical insurance providers.

In October 2021, the World Health Organization recommended RTS,S/AS01 (RTS,S), the world’s first malaria vaccine. This vaccine works against the P. falciparum malaria parasite. It can lower the rate of serious and life-threatening malaria for children in areas with moderate to high rates of the disease. If used widely, the malaria vaccine could save tens of thousands of lives every year. But the WHO only recommends it for kids in certain areas of the world.

Children as young as 5 months old who are at risk for malaria will get the vaccine in four separate doses.

Experts have found that the vaccine could have major public health benefits. Models show that use of RTS,S can prevent one death for every 200 fully vaccinated children.

But the shot still isn’t as successful at disease control as most childhood vaccinations. Because of this, countries at high risk can’t rely just on the vaccine to stop the threat of malaria. But when it’s used with other prevention methods, like insecticide-treated bed nets, pesticides, and other remedies, the vaccine can greatly reduce illness and death from the disease.

Experts continue to plan long-term and sustainable methods to keep up supply of the malaria vaccine. This includes ways to make the vaccination more cost-effective, practical, and helpful for those most at risk.

Two other vaccine options, the PfSPZ and R21 malaria vaccines, also show some promise.

Show Sources

SOURCES:

CDC: "Malaria," “Malaria: Frequently Asked Questions,” “About Malaria,” “Where Malaria Occurs,” “Malaria Information and Prophylaxis, by Country,” “Choosing a Drug To Prevent Malaria,” “Malaria’s Impact Worldwide,” “Treatment of Malaria: Guidelines for Clinicians,” "Malaria Diagnosis (United States)," "Malaria Diagnosis (U.S.) – Serology,” “Malaria Vaccine Recommended for Broader Use by WHO: “Best Thing Since Bed Nets," "Traveling? Make Sure You Protect Yourself from Malaria," "Locally Acquired Malaria Cases Identified in the United States," "Getting Health Care During Travel." 

Medline Plus: “Malaria.”

World Health Organization: “Malaria,” “Q&A on RTS,S malaria vaccine," "WHO recommends groundbreaking malaria vaccine for children at risk."

American Academy of Family Physicians: “Malaria.”

Medecins Sans Frontieres: “Malaria.”

Mayo Clinic: “Malaria.”

National Health Services: “Malaria.”

Stanford Medicine: "Types of Malaria Parasites."

National Organization for Rare Disorders: “Rare Disease Database: Malaria.”

FDA: "FDA Approves Only Drug in U.S. to Treat Severe Malaria."

Malaria Consortium: “Artemisinin-based Combination Therapy.”

Lab Tests Line: “Malaria.”

Cleveland Clinic: "Malaria."

Malaria Vaccine Initiative: “RTS,S.”

Human Vaccines and Immunotherapeutics: “RTS,S/AS01 vaccine (Mosquirix™): an overview."

U.S. Environmental Protection Agency: "Find the Repellent that is Right for You."

 

 

 

 

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