HEALTH TALKS

MALARIA OVERVIEW

Overview

Malaria is a disease caused by a parasite. The parasite is transmitted to humans through the bites of infected mosquitoes. People who have malaria usually feel very sick, with a high fever and shaking chills. Each year, approximately 210 million people are infected with malaria, and about 440,000 people die from the disease. Most of the people who die from the disease are young children in Africa.

While the disease is uncommon in temperate climates, malaria is still common 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 steps to prevent mosquito bites by wearing protective clothing, using insect repellants and sleeping under treated mosquito nets. Depending on the area you are visiting and your individual risk factors for infection, you may also want to take preventive medicine before, during and after your trip. Many malaria parasites are now resistant to the most common drugs used to treat the disease.

Symptoms

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.

When to see a doctor

Talk to your doctor if you experience a 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

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  Malaria transmission cycle

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

Risk factors

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.

Complications

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.

Malaria may recur

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

Prevention

If you live in or are traveling to an area where malaria is common, take steps to avoid mosquito bites. Mosquitoes are most active between dusk and dawn. To protect yourself from mosquito bites, you should:

• Cover your skin. Wear pants and long-sleeved shirts.
• Apply insect repellant to skin and clothing. Sprays containing DEET can be used on skin and sprays containing permethrin are safe to apply to clothing.
• Sleep under a net. Bed nets, particularly those treated with insecticide, help prevent mosquito bites while you are sleeping.

Preventive medicine

If you're going to be traveling to a location where malaria is common, talk to your doctor a few months ahead of time about whether you should take drugs before, during and after your trip to help protect you from malaria parasites.

In general, the drugs taken to prevent malaria are the same drugs used to treat the disease. Your doctor needs to know when and where you'll be traveling so that he or she can help you evaluate your risk for infection and, if necessary, prescribe the drug that will work best on the type of malaria parasite most commonly found in that region.