A malaria infection is generally characterized by the following signs and symptoms:

• Fever
• Chills
• Headache
• Nausea and vomiting
• Muscle pain and fatigue

Other signs and symptoms may include:

• Sweating
• Chest or abdominal pain
• Cough

Some people who have malaria experience cycles of malaria "attacks." An attack usually starts with shivering and chills, followed by a high fever, followed by sweating and a return to normal temperature. Malaria signs and symptoms typically begin within a few weeks after being bitten by an infected mosquito. However, some types of malaria parasites can lie dormant in your body for up to a year.

Malaria is caused by a type of microscopic parasite. The parasite is transmitted to humans most commonly through mosquito bites.

Mosquito transmission cycle

• Uninfected mosquito. A mosquito becomes infected by feeding on a person who has malaria.
• Transmission of parasite. If this mosquito bites you in the future, it can transmit malaria parasites to you.
• In the liver. Once the parasites enter your body, they travel to your liver — where some types can lie dormant for as long as a year.
• Into the bloodstream. When the parasites mature, they leave the liver and infect your red blood cells. This is when people typically develop malaria symptoms.
• On to the next person. If an uninfected mosquito bites you at this point in the cycle, it will become infected with your malaria parasites and can spread them to the other people it bites.

Other modes of transmission

Because the parasites that cause malaria affect red blood cells, people can also catch malaria from exposure to infected blood, including:

• From mother to unborn child
• Through blood transfusions
• By sharing needles used to inject drugs

The biggest risk factor for developing malaria is to live in or to visit areas where the disease is common. There are many different varieties of malaria parasites. The variety that causes the most serious complications is most commonly found in:

• African countries south of the Sahara Desert
• The Asian subcontinent
• New Guinea, the Dominican Republic and Haiti

Risks of more-severe disease

People at increased risk of serious disease include:

• Young children and infants
• Older adults
• Travelers coming from areas with no malaria
• Pregnant women and their unborn children

Poverty, lack of knowledge, and little or no access to health care also contribute to malaria deaths worldwide.

Immunity can wane

Residents of a malaria region may be exposed to the disease so frequently that they acquire a partial immunity, which can lessen the severity of malaria symptoms. However, this partial immunity can disappear if you move to a country where you're no longer frequently exposed to the parasite.

Malaria can be fatal, particularly malaria caused by the variety of parasite that's common in tropical parts of Africa. The Centers for Disease Control and Prevention estimates that 91 percent of all malaria deaths occur in Africa — most commonly in children under the age of 5.

In most cases, malaria deaths are related to one or more serious complications, including:

• Cerebral malaria. If parasite-filled blood cells block small blood vessels to your brain (cerebral malaria), swelling of your brain or brain damage may occur. Cerebral malaria may cause seizures and coma.
• Breathing problems. Accumulated fluid in your lungs (pulmonary edema) can make it difficult to breathe.
• Organ failure. Malaria can cause your kidneys or liver to fail, or your spleen to rupture. Any of these conditions can be life-threatening.
• Anemia. Malaria damages red blood cells, which can result in anemia.
• Low blood sugar. Severe forms of malaria itself can cause low blood sugar (hypoglycemia), as can quinine — one of the most common medications used to combat malaria. Very low blood sugar can result in coma or death.