Malaria is a serious infection spread by mosquitoes that causes fever, chills, and flu-like illness

Malaria is caused by a parasite—a tiny organism that lives inside mosquitoes and enters your body through a mosquito bite. Once in your bloodstream, the parasite travels to your liver and then to your red blood cells, where it multiplies. This causes the symptoms most people recognize: high fever, severe chills, sweating, headache, muscle aches, and nausea. The illness typically starts 7 to 30 days after infection, though it can take longer.

The disease is not spread from person to person through touch, coughing, or sharing food. Only certain mosquitoes—the Anopheles mosquito, which bites mainly at night—can carry and spread malaria. This means you cannot catch malaria from someone who has it unless that person's blood enters your body (which almost never happens outside of blood transfusions or needle sharing).

Malaria kills more than 600,000 people worldwide each year, mostly children under five in Africa. In the United States, malaria is rare because mosquito control and air conditioning have reduced the mosquitoes that carry it. Most U.S. cases occur in people who traveled to countries where malaria is common and were bitten there.

Key Takeaways

  • Malaria is caused by a parasite transmitted through the bite of an infected Anopheles mosquito, not through contact with an infected person.
  • Symptoms include high fever, chills, sweating, headache, and muscle aches, usually appearing 7 to 30 days after infection.
  • A blood test is the only way to diagnose malaria; doctors look for the parasite under a microscope or use a rapid test.
  • Malaria is treatable with prescription medications, and treatment works best when started early.
  • Prevention in high-risk areas involves mosquito nets, insect repellent, and sometimes preventive medication before travel.

How the parasite enters your body and causes illness

When an infected mosquito bites you, it injects saliva containing the malaria parasite into your skin. The parasite enters your bloodstream and travels to your liver, where it hides and multiplies for 7 to 30 days without causing symptoms. This is called the incubation period. During this time, you feel fine and may not know you are infected.

After the parasite multiplies in the liver, it breaks out and invades your red blood cells. As it destroys these cells, your body releases chemicals that cause fever and chills. The fever often spikes in a pattern—some types of malaria cause fever every other day, while others cause it daily. This cycle of fever, chills, and sweating can last for hours and then stop, making people think they are recovering, only to have it return.

If untreated, malaria can damage your organs, cause severe anemia (low red blood cell count), lead to brain swelling, or trigger kidney failure. Pregnant women and young children are at highest risk for severe illness. In some cases, malaria can be fatal within days of the first symptoms.

Who is at risk for malaria

People living in or traveling to countries where malaria is common face the highest risk. Malaria is endemic—meaning it spreads regularly—in parts of Africa, South Asia, Southeast Asia, Central America, and South America. The risk is highest in rural areas near standing water, where mosquitoes breed, and in regions with warm, wet climates year-round.

Certain groups have worse outcomes if infected. Children under five, pregnant women, people with HIV or AIDS, and travelers from malaria-free countries (who have no immunity) are more likely to develop severe illness. People with sickle cell disease have some natural protection against malaria but still need treatment if infected.

In the United States, your risk is very low unless you travel. The mosquitoes that carry malaria do not survive in most of the country's climate, and mosquito control programs have eliminated them from areas where they once lived. However, malaria cases do occur in the U.S. in people who were infected abroad and did not know they had it.

How doctors identify malaria

A doctor diagnoses malaria by finding the parasite in your blood. The standard test is a blood smear: a lab technician places a drop of your blood on a glass slide, stains it with dye, and looks for the parasite under a microscope. This test is reliable but requires skill and can take several hours. A doctor may order multiple blood smears taken at different times, because the parasite levels in your blood rise and fall in cycles.

Many clinics and hospitals also use rapid diagnostic tests, which detect parasite proteins in your blood in 15 to 20 minutes. These tests are faster but slightly less accurate than blood smears. A positive rapid test is usually confirmed with a blood smear to identify which type of malaria parasite you have, because different types require different treatments.

If you have traveled to a malaria region and develop fever, chills, or flu-like symptoms weeks or even months after returning home, tell your doctor about the travel. Malaria can be easy to miss because its symptoms resemble the flu or other common infections. A doctor who knows you may have been exposed will order the right blood tests.

Treatment and recovery

Malaria is treated with prescription antimalarial medications. The specific drug depends on which type of malaria parasite you have, where you were infected, and whether the parasite in that region is resistant to certain drugs. Common medications include chloroquine, artemether, quinine, and atovaquone-proguanil. Treatment usually lasts three to seven days, and most people recover fully if treated early.

During treatment, you will likely feel very ill for the first few days as your body clears the parasites from your blood. Fever may spike before it drops. You may need to stay in a hospital if your malaria is severe or if you have complications like organ damage. Doctors will monitor your blood counts, kidney function, and liver function during and after treatment.

After recovery, you do not develop lasting immunity to malaria. You can be infected again if bitten by another infected mosquito. People who live in malaria regions their whole lives develop partial immunity over time, which reduces the severity of illness but does not prevent reinfection.

Prevention in high-risk areas

If you travel to a region where malaria is common, your doctor may prescribe preventive medication to take before, during, and after your trip. These medications suppress the parasite if you are bitten, preventing illness. The type of medication depends on where you are traveling, how long you will be there, and your health history. You must start the medication before you arrive and continue it for a set time after you leave.

Beyond medication, the most effective prevention is avoiding mosquito bites. Sleep under an insecticide-treated bed net, wear long sleeves and pants during dawn and dusk (when Anopheles mosquitoes bite), and use insect repellent containing DEET on exposed skin. Air conditioning and screened windows reduce mosquito entry into buildings. Draining standing water around your home eliminates breeding sites.

No vaccine for malaria is widely available yet, though one vaccine called RTS,S has been approved in some African countries and shown modest protection in children. Most travelers rely on medication and mosquito avoidance rather than vaccination.

What happens if malaria is not treated

Untreated malaria becomes progressively more dangerous. The parasite continues to multiply and destroy red blood cells, causing severe anemia. Your organs—especially the brain, kidneys, and liver—may fail. Cerebral malaria, in which the parasite damages blood vessels in the brain, causes seizures, coma, and death. Severe malaria can also cause acute respiratory distress, where your lungs fill with fluid and you cannot breathe without help.

Even if you survive untreated malaria, the damage can be permanent. Some people develop long-term neurological problems, kidney disease, or chronic anemia. Pregnant women who are not treated risk miscarriage, stillbirth, or giving birth to a baby with low birth weight or congenital malaria (infection present at birth).

The good news is that malaria responds well to treatment when caught early. If you develop fever, chills, or flu-like symptoms after traveling to a malaria region, seek medical care immediately and mention your travel history. Early diagnosis and treatment prevent serious complications and save lives.

Frequently Asked Questions

Can you get malaria twice?

Yes. Malaria does not create lasting immunity, so you can be infected again if bitten by another infected mosquito. People living in malaria regions develop partial immunity over years of repeated exposure, which reduces symptom severity but does not prevent reinfection. Travelers have no immunity and can catch malaria on any trip to a high-risk area.

How long does malaria last if untreated?

Untreated malaria can last weeks to months and become life-threatening within days. Some types of malaria cause recurring fever cycles that continue until the parasite is cleared or the person dies. Without treatment, severe malaria can cause organ failure and death within one to two weeks of symptom onset.

Is malaria contagious from person to person?

No. Malaria spreads only through mosquito bites, not through touch, coughing, sharing food, or any other contact with an infected person. The only exceptions are blood transfusions or needle sharing, which are extremely rare routes of transmission outside of healthcare settings.

What should I do if I think I have malaria?

See a doctor or go to an emergency room immediately. Tell them you may have malaria and mention any recent travel to malaria regions. A blood test can confirm or rule out malaria within hours. Early treatment is critical and highly effective at preventing serious illness.

Do I need preventive medication if I travel to a malaria region?

Most people traveling to malaria regions should take preventive medication, but the decision depends on where you are going, how long you will stay, and your health history. Talk to a travel medicine doctor or your regular doctor at least four to six weeks before your trip. They can assess your risk and recommend the right prevention strategy for you.