Malaria is a blood infection spread by mosquitoes, not by contact with other people

Malaria happens when a mosquito carrying a parasite bites you and injects that parasite into your bloodstream. The parasite travels to your liver, multiplies there, then enters your red blood cells and destroys them. This is why malaria causes fever, chills, and anemia—your body is losing red blood cells faster than it can replace them. You cannot catch malaria from another person's cough, touch, or blood; only an infected mosquito can transmit it.

The mosquitoes that carry malaria are Anopheles mosquitoes, and they bite mostly at night. They are found in tropical and subtropical regions—parts of Africa, Southeast Asia, Central and South America, and the Middle East. If you live in or travel to one of these areas, you are at risk. If you live in a temperate climate where these mosquitoes do not survive, your risk is very low.

Key Takeaways

  • Malaria is caused by a parasite injected through a mosquito bite, not spread person-to-person.
  • The parasite multiplies in your liver first, then attacks your red blood cells, causing fever and anemia.
  • Anopheles mosquitoes bite mainly at night and live only in warm climates.
  • Symptoms usually appear 7 to 30 days after infection, though some parasites can lie dormant for months or years.

How the parasite enters your body and what it does

When an infected Anopheles mosquito bites you, it injects saliva containing parasites called Plasmodium. These parasites are too small to see without a microscope. They travel through your bloodstream to your liver within minutes.

In your liver, the parasites multiply rapidly for 7 to 30 days without causing symptoms. You feel fine during this time, but the parasites are preparing to attack your blood cells. Once they enter your red blood cells, they feed on the cell contents and multiply again. When the infected cell bursts, it releases thousands of new parasites into your blood, and this is when you start to feel sick. Your body's immune response to the bursting cells causes the fever, chills, and body aches.

There are five species of Plasmodium that infect humans. Plasmodium falciparum causes the most severe form of malaria and is responsible for most malaria deaths. Plasmodium vivax and Plasmodium ovale can stay dormant in your liver for months or years, causing relapses long after your first infection seemed to end.

What symptoms look like and when they start

Malaria symptoms usually begin 7 to 30 days after the mosquito bite, though this can vary. Early signs are easy to confuse with flu: fever, headache, muscle aches, fatigue, and nausea. Some people have chills so severe they shake uncontrollably.

As the infection progresses, fevers often come in cycles. You might have a high fever for several hours, then sweat heavily as it breaks, then feel fine for a few hours before the fever returns. This pattern repeats because new batches of parasites are bursting from your red blood cells on a schedule. In severe malaria, the fever does not follow a pattern—it stays high and constant.

Severe malaria can cause confusion, seizures, organ failure, severe anemia, and coma. Cerebral malaria, where the parasite damages the brain, is life-threatening. If you have been in a malaria region and develop fever, chills, or body aches, you need a blood test to rule out malaria, even if symptoms seem mild.

Why some people get sicker than others

Your age, previous malaria infections, and genetics all affect how severe your case becomes. Young children and pregnant women are at highest risk for severe malaria. Adults who grew up in malaria regions often develop partial immunity—they can still get infected, but their symptoms are usually milder and they recover faster.

People with sickle cell disease have some natural protection against malaria because the parasite cannot survive as well in their red blood cells. People with HIV or other conditions that weaken the immune system are more likely to develop severe malaria. If you have no immunity and no prior exposure, your first infection is more likely to be serious.

Where malaria is found and who is at risk

Malaria exists in over 100 countries, mostly in Africa, Asia, and Latin America. Sub-Saharan Africa carries the highest burden—about 95 percent of malaria deaths worldwide occur there. Within these regions, malaria is more common in rural areas and during rainy seasons when mosquitoes breed more.

Your risk depends on where you are going, when you are going, and what precautions you take. If you travel to a malaria region, you can reduce your risk by using insect repellent, sleeping under a bed net, wearing long sleeves at night, and taking antimalarial medication before, during, and after your trip. If you live in a malaria region, your risk is constant unless you use these same protections consistently.

How malaria is diagnosed and treated

Malaria is diagnosed with a blood test. A lab technician looks at a blood sample under a microscope to see if parasites are present, or uses a rapid test that detects parasite proteins. If you have been in a malaria region and have fever, your doctor should order this test.

Treatment depends on which Plasmodium species you have and where you were infected, because some parasites have developed resistance to certain drugs. Antimalarial medications kill the parasites in your blood and liver. Most cases of uncomplicated malaria can be treated as an outpatient with oral medication, though severe malaria requires hospitalization and intravenous drugs. Treatment usually lasts 3 to 7 days, and most people recover fully if they receive treatment early.

Prevention and what to do if you have been exposed

If you are traveling to a malaria region, talk to your doctor at least 4 weeks before your trip. Your doctor can prescribe antimalarial medication suited to the specific region and your health history. You take this medication before you leave, during your stay, and for a period after you return. This medication does not prevent infection entirely, but it stops the parasite from multiplying and causing illness.

Insect repellent containing DEET, picaridin, or oil of lemon eucalyptus reduces mosquito bites. Bed nets treated with insecticide are highly effective, especially in areas where malaria is common. Wearing long sleeves and pants during dawn and dusk—when Anopheles mosquitoes bite—also helps.

If you develop fever within 3 months of returning from a malaria region, tell your doctor where you traveled. Malaria can appear weeks or even months after you leave the region, and some types can relapse years later. A blood test is the only way to know for certain.

Frequently Asked Questions

Can you get malaria twice?

Yes. Malaria infection does not create permanent immunity. You can be infected multiple times in your life. People who live in malaria regions may have partial immunity after repeated infections, but they can still get sick. Some types of malaria can also relapse months or years after your first infection because the parasite hides in your liver.

Is malaria contagious from person to person?

No, malaria is not spread by coughing, touching, or sharing blood. Only an infected mosquito can transmit it. A pregnant woman can pass malaria to her unborn child, and malaria can be transmitted through blood transfusion or shared needles, but casual contact with a person who has malaria carries no risk.

What happens if malaria is not treated?

Untreated malaria can become severe and life-threatening. The parasite continues to destroy red blood cells, causing severe anemia, organ damage, and brain damage. Severe malaria kills about 15 to 20 percent of people who develop it, even with treatment. Early treatment with antimalarial drugs is highly effective and prevents complications.

Can you get malaria from a blood transfusion?

Yes, but this is rare in countries with strict blood screening. Blood banks in the United States and Europe screen all donated blood for malaria parasites. In regions where malaria is common, blood screening may be less rigorous, so transfusion risk is higher. If you have had malaria, you may be deferred from donating blood for a period.