Malaria

Malaria is a disease caused by a parasite, transmitted by the bite of infected mosquitoes. Malaria produces recurrent attacks of chills and fever. Malaria kills an estimated 660,000 people each year.

While the disease is uncommon in temperate climates, malaria is still prevalent in tropical and subtropical countries. World health officials are trying to reduce the incidence of malaria by distributing bed nets to help protect people from mosquito bites as they sleep. Scientists around the world are working to develop a vaccine to prevent malaria.

If you’re traveling to locations where malaria is common, take preventive medicine before, during and after your trip. Many malaria parasites are now immune to the most common drugs used to treat the disease.

Symptoms

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

• Moderate to severe shaking chills
• High fever
• Sweating

Other signs and symptoms may include:

• Headache
• Vomiting
• Diarrhea

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.

When to see a doctor

Talk to your doctor if you experience a high fever while living in or after traveling to a high-risk malaria region. The parasites that cause malaria can lie dormant in your body for up to a year. If you have severe symptoms, seek emergency medical attention.

Causes

Malaria is caused by a type of microscopic parasite that’s transmitted most commonly by mosquito bites.

Mosquito transmission cycle

• Uninfected mosquito. A mosquito becomes infected by feeding on a person who has malaria.
• Transmission of parasite. If you’re the next person this mosquito bites, it can transmit malaria parasites to you.
• In the liver. The parasites then 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 next person it bites.

Other modes of transmission

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

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

Risk factors

The biggest risk factor for developing malaria is to live in or to visit tropical areas where the disease is common. Many different subtypes of malaria parasites exist. The variety that causes the most lethal complications is most commonly found in:

• African countries south of the Sahara Desert
• The Asian subcontinent
• Solomon Islands, Papua New Guinea and Haiti

Risks of more severe disease

People at increased risk of serious disease include:

• Young children and infants
• 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.

Complications

Malaria can be fatal, particularly the variety that’s common in tropical parts of Africa. The Centers for Disease Control and Prevention estimate that 90 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 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.
• Malaria damages red blood cells, which can result in anemia.
• Low blood sugar. Severe forms of malaria itself can cause low blood sugar, as can quinine — one of the most common medications used to combat malaria. Very low blood sugar can result in coma or death.

Malaria may recur

Some varieties of the malaria parasite, which typically cause milder forms of the disease, can persist for years and cause relapses.