Seattle Malaria Clinical Trials Center (Seattle MCTC)

Malaria FAQ

malaria biting human

Photo by James Gathany / CDC file

What is malaria?

Malaria is a serious and sometimes fatal disease caused by a parasite that commonly infects a certain type of mosquito which feeds on humans. People who get malaria are typically very sick with high fevers, shaking chills, and flu‐like illness. Five kinds of malaria parasites can infect humans: Plasmodium falciparum, P. vivax, P. ovale, P. knolesi, and P. malariae. Infection with P. falciparum, if not promptly treated, may lead to death. Although malaria can be a deadly disease, illness and death from malaria can usually be prevented and is easily treated.

How is malaria transmitted?

Usually, people get malaria by being bitten by an infective female Anopheles mosquito. Only Anopheles mosquitoes can transmit malaria, and they must have been infected through a previous blood meal taken on an infected person. When a mosquito bites an infected person, a small amount of blood is taken in which contains microscopic malaria parasites. About 1 week later, when the mosquito takes its next blood meal, these parasites mix with the mosquito's saliva and are injected into the person being bitten.

Because the malaria parasite is found in red blood cells of an infected person, malaria can also be transmitted through blood transfusion, organ transplant, or the shared use of needles or syringes contaminated with blood. Malaria may also be transmitted from a mother to her unborn infant before or during delivery (congenital malaria).

Is malaria a contagious disease?

No. Malaria is not spread from person to person like a cold or the flu, and it cannot be sexually transmitted. You cannot get malaria from casual contact with malaria‐infected people, such as sitting next to someone who has malaria.

Who is at risk for malaria?

Anyone can get malaria. Most cases occur in people who live in countries with mosquito infestation. People from countries with no malaria can become infected when they travel to countries with malaria or through a blood transfusion (although this is very rare). Also, an infected mother can transmit malaria to her infant before or during delivery.

Who are the people that are at most risk for getting sick and dying from malaria?

Plasmodium falciparum causes severe and life‐threatening malaria; this parasite is very common in many countries in Africa south of the Sahara desert. People who are heavily exposed to the bites of mosquitoes infected with P. falciparum are most at risk of dying from malaria. People who have little or no immunity to malaria, such as young children and pregnant women or travelers coming from areas with no malaria, are more likely to become very sick and die. Poor people living in rural areas who lack knowledge, money or access to health care are at greater risk for this disease. As a result of all these factors, an estimated 90 percent of deaths due to malaria occur in Africa south of the Sahara (sub‐Saharan Africa); most of these deaths occur in children under 5 years of age. Participants in our trials are followed very carefully once they are enrolled into our studies for all of these reasons.

If diagnosed with malaria and cured, am I protected from malaria infection in the future?

No, anyone who goes to a malaria‐risk country should take precautions against contracting malaria. Usually, people who live in malaria‐endemic areas have some immunity to malaria. However, without frequent exposure to malaria parasites, your immune system loses its ability to fight malaria. You are as much at risk as a nonimmune person. Please consult with your health care provider or a travel clinic about precautions to take against malaria (preventive drugs and protection against mosquito bites) and against other diseases.

What kinds of symptoms will be experienced if infected with malaria?

Symptoms of malaria include fever and flu‐like illness, including shaking chills, headache, muscle aches and tiredness. Nausea, vomiting and diarrhea may also occur. Most participants in our studies do not feel sick.

What will happen if the malaria infection is not treated?

Malaria may cause anemia and jaundice (yellow coloring of the skin and eyes) because of the loss of red blood cells. Infection with one type of malaria, Plasmodium falciparum, if not promptly treated, may cause kidney failure, seizures, mental confusion, coma and death.

How soon will a person feel sick once infected with malaria?

For most people, symptoms begin 10 days to 4 weeks after infection, although a person may feel ill as early as 7 days or as late as 1 year later. Two kinds of malaria, P. vivax and P. ovale, can occur again (relapsing malaria). In P. vivax and P. ovale infections, some parasites can remain dormant in the liver for several months up to about 4 years after a person is bitten by an infected mosquito. When these parasites come out of hibernation and begin invading red blood cells (relapse), the person will become sick.

To learn more about malaria, please visit the Centers for Disease Control and Prevention or World Health Organization.