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Malaria

Malaria [muh-LARE-ee-uh] is a long-lasting disease of the blood. It is transmitted to people by mosquitoes infected with the malaria parasite. The malaria parasite attacks the blood and causes recurring chills, fever, and sometimes jaundice and anemia. Malaria is very common throughout the world. In the United States, the main risk is to persons traveling to tropical and subtropical countries where malaria is a problem. No vaccine against malaria is available. Travelers can protect themselves by using anti-mosquito measures and by taking drugs to prevent malaria.

\What is malaria?

Malaria is a disease of the blood that is transmitted to people by infected mosquitoes. Malaria is very common throughout the world. In the United States, the main risk is to persons traveling to tropical and subtropical countries where malaria is a problem.

What is the infectious agent that causes malaria?

Malaria is caused by any one of four species of one-celled parasites, called Plasmodium. The parasite is spread to people by the female Anopheles mosquito, which feeds on human blood. Although four species of malaria parasites can infect humans and cause illness, only malaria caused by Plasmodium falciparum is potentially life-threatening.

Where is malaria found?

Malaria transmission occurs in large areas of Central and South America, sub-Saharan Africa, the Indian subcontinent, Southeast Asia, the Middle East, and Oceania. The risk to travelers varies depending on local weather conditions, the number of mosquitoes in the area, and the traveler's itinerary and time and type of travel.

How is malaria spread?

A person gets malaria from the bite of an infected female mosquito. The mosquito bite injects young forms of the malaria parasite into the person's blood. The parasites travel through the person's bloodstream to the liver, where they grow to their next stage of development. In 6 to 9 days, the parasites leave the liver and enter the bloodstream again. They invade the red blood cells, finish growing, and begin to multiply quickly. The number of parasites increases until the red blood cells burst, releasing thousands of parasites into the person's bloodstream. The parasites attack other red blood cells, and the cycle of infection continues, causing the common signs and symptoms of malaria.

When a non-infected mosquito bites an infected person, the mosquito sucks up parasites from the person's blood. The mosquito is then infected with the malaria parasites. The parasites go through several stages of growth in the mosquito. When the mosquito bites someone else, that person will become infected with malaria parasites, and the cycle will begin again.

Malaria parasites can also be transmitted by transfusion of blood from an infected person or by the use of needles or syringes contaminated with the blood of an infected person.

What are the signs and symptoms of malaria?

People with malaria typically have cycles of chills, fever, and sweating that recur every 1, 2, or 3 days. The attack of the malaria parasites on the person's red blood cells makes the person's temperature rise and the person feel hot. The subsequent bursting of red blood cells makes the person feel cold and have hard, shaking chills. Nausea, vomiting, and diarrhea often go along with the fever. The destruction of red blood cells can also cause jaundice (yellowing of the skin or whites of the eyes) and anemia.

How soon after exposure do symptoms appear?

The time between a mosquito bite and the start of illness is usually 7 to 21 days, but some types of malaria parasites take much longer to cause symptoms. When infection occurs by blood transfusion, the time to the start of symptoms depends on the number of parasites in the transfusion.

How is malaria diagnosed?

Malaria is diagnosed by a blood test to check for parasites.

Who is at risk for malaria?

Anyone who lives in or travels to a country where there are malaria-infected people and mosquitoes is at risk.

What complications can result from malaria?

Malaria caused by Plasmodium falciparum can cause kidney or liver failure, coma, and death. Although infections with other malaria parasites cause less serious illness, parasites can remain inactive in the liver and cause a reappearance of symptoms months or even years later.

What is the treatment for malaria?

The treatment for malaria depends on where a person is infected with the disease. Different areas of the world have malaria types that are resistant to certain medicines. The correct drugs for each type of malaria must be prescribed by a doctor.

Infection with Plasmodium falciparum is a medical emergency. About 2% of persons infected with falciparum malaria die, usually because of delayed treatment.

How common is malaria?

Worldwide, an estimated 200 million to 300 million malaria infections occur each year, with 2 million to 3 million deaths. Most deaths are from infection with Plasmodium falciparum.

About 1,200 cases of malaria are diagnosed in the United States each year. Most are in persons entering the country for the first time or returning from foreign travel. A very small number of cases are the result of direct transmission involving mosquitoes that live in the United States. Most of these have occurred in Mexican farm workers living in California in poor conditions.

Is malaria an emerging infectious disease?

Yes. Many countries have been experiencing a resurgence in cases caused by Plasmodium falciparum, the most deadly of the four human malaria parasites. Urban migration, poverty, and poor sanitation have returned malaria to cities where it once was eliminated. New roads, logging, and irrigation have drawn people into once-isolated areas where mosquitoes thrive. Refugees, migrants, and tourists have spread the disease across borders.

The seriousness of the worldwide re-emergence of malaria is made worse by the spread of parasites that are resistant to anti-malaria drugs. Parasites, like bacteria and viruses, can develop resistance to the drugs used to prevent or treat infection. Malaria parasites are increasingly resistant to chloroquine, the drug most widely used for prevention and treatment. Chloroquine-resistant strains have been reported from areas in Africa, Asia, and the Americas.

The potential also exists for malaria to become re-established in the United States. Currently, about 1,200 malaria cases are reported each year in the United States. Almost all occur in persons who were infected in other parts of the world (imported malaria). Small outbreaks of non-imported malaria, the result of transmission from imported cases, have also been reported. So far, the outbreaks have been quickly and easily contained. A continued increase in drug-resistant malaria throughout the world, however, could increase the number of cases of imported malaria and improve the chances for malaria to re-emerge in the United States.

How can malaria be prevented?

No vaccine against malaria is available. Travelers can protect themselves by using anti-mosquito measures and by taking drugs to prevent malaria.

1. Avoid mosquito bites -- Avoiding the bites of Anopheles mosquitoes is the best way to prevent infection. Because Anopheles mosquitoes feed at night, malaria transmission happens mainly between dusk and dawn. Travelers should take steps to reduce contact with mosquitoes both when outdoors and inside, especially during these hours.

When outside: Wear long-sleeved clothing and long pants. For extra protection, treat clothing with the insecticide permethrin.

Use insect repellent on exposed skin. The most effective repellents contain 20% to 35% DEET (N,N-diethylmethyltoluamide). Follow application instructions carefully when using these products.

When inside: Stay in well-screened areas as much as possible during the evening.

Spray living and sleeping areas with insecticide.

Use a bednet when sleeping in a room that is not screened or air conditioned. For extra protection, treat the bednet with the insecticide permethrin.

2. Take anti-malaria drugs -- When traveling to an area known to have malaria, discuss your travel plans with a doctor well before departure. Medicines to prevent malaria are usually prescribed for persons traveling to areas where malaria is common. Travelers from different countries might receive different recommendations because of differences in the availability of medicines. Travelers visiting only cities or rural areas where there is no risk of malaria might not need preventive drugs. An exact itinerary is needed to decide on the right degree of protection.

To be sure that your anti-malaria drug helps protect you against malaria, you must follow the recommended doses and schedules exactly:

Take pills on the same day each week, or, for pills to be taken daily, at the same time each day. Take pills after meals. Take the recommended doses 1 to 2 weeks before travel, throughout the trip, and for 4 weeks after leaving the area with malaria. Do not stop taking the pills after arriving home. Complete the full dosage.

Travelers should understand that they can get malaria even if they use anti-malaria drugs. Pregnant women and young children need special instructions because of the potential effects of malaria illness and the danger in using some drugs for malaria prevention and treatment.

3. Seek medical help in case of illness -- Symptoms of malaria can be mild. Travelers should suspect malaria if they experience an unexplained fever while in or after returning from an area where malaria is common. Persons with suspected malaria should get medical help right away.