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Malaria

Malaria is a mosquito-borne disease caused by a parasite. People with malaria often experience fever, chills, and flu-like illness. Left untreated, they may develop severe complications and die. Each year 350-500 million cases of malaria occur worldwide, and over one million people die, most of them young children in Africa south of the Sahara.

This sometimes fatal disease can be prevented and cured. Bednets, insecticides, and antimalarial drugs are effective tools to fight malaria in areas where it is transmitted. Travelers to a malaria-risk area should avoid mosquito bites and take a preventive antimalarial drug.

 

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. Four kinds of malaria parasites can infect humans: Plasmodium falciparum, P. vivax, P. ovale, 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.

About 1,300 cases of malaria are diagnosed in the United States each year. The vast majority of cases in the United States are in travelers and immigrants returning from malaria-risk areas, many from sub-Saharan Africa and South Aisa.

The World Health Organization estimates that each year 300-500 million cases of malaria occur and more than 1 million people die of malaria, especially in developing countries. Most deaths occur in young children. For example, in Africa, a child dies from malaria every 30 seconds. Because malaria causes so much illness and death, the disease is a great drain on many national economies. Since many countries with malaria are already among the poorer nations, the disease maintains a vicious cycle of disease and poverty.

Key facts

  • Malaria is a life-threatening disease caused by parasites that are transmitted to people through the bites of infected mosquitoes.
  • A child dies of malaria every 30 seconds.
  • There were 247 million cases of malaria in 2006, causing nearly one million deaths, mostly among African children.
  • Malaria is preventable and curable.
  • Approximately half of the world's population is at risk of malaria, particularly those living in lower-income countries.
  • Travellers from malaria-free areas to disease "hot spots" are especially vulnerable to the disease.
  • Malaria takes an economic toll - cutting economic growth rates by as much as 1.3% in countries with high disease rates.

The following interventions need to be delivered worldwide by 2010:

  • More than 700 million insecticide-treated bednets – half of those in Africa
  • More than 200 million of doses of effective treatment
  • Indoor spraying for around 200 million homes annually
  • Approximately 1.5 billion diagnostic tests annually

What it will cost

  • In 2009, roughly $5.3 billion will be needed for malaria control worldwide
  • In 2010, $6.2 billion will be needed
  • From 2011 to 2020, roughly $5 billion per year will be need to sustain the gains of control measures.
  • In addition, about $1 billion per year will be needed for research and development of new prevention and treatment tools

What will be the impact

A dramatically expanded access to core anti-malaria interventions (protective nets, spraying, diagnostics and effective drugs) will result in a sharp decline of malaria cases and deaths. However, these measures will not eliminate the mosquito vector, the parasite or the favorable environmental conditions for transmission in many countries and regions. In some countries with naturally high transmission rates, control measures may need to be maintained for 15- 20 years or longer until new tools enabling elimination are developed or new research indicates that control measures can be safely reduced without risk of resurgence.

Malaria is caused by parasites of the species Plasmodium. The parasites are spread to people through the bites of infected mosquitoes.

There are four types of human malaria:

  • Plasmodium falciparum
  • Plasmodium vivax
  • Plasmodium malariae
  • Plasmodium ovale.

Plasmodium falciparum and Plasmodium vivax are the most common. Plasmodium falciparum is the most deadly.

 

How People Get Malaria (Transmission)

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

Who is at risk for malaria?

Anyone can get malaria. Most cases occur in people who live in countries with malaria transmission. 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 most at risk of getting very 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% of deaths due to malaria occur in Africa south of the Sahara; most of these deaths occur in children under 5 years of age.

 

If I was born in a country where malaria is present and had malaria as a child, then moved to the United States many years ago; do I need to worry about getting malaria when I return home to visit my friends and relatives?

Yes, anyone who goes to a malaria-risk country should take precautions against contracting malaria. During the last several years that you have spent in the United States, you have lost any malaria immunity that you might have had while living in your native country. Without frequent exposure to malaria parasites, your immune system has lost its ability to fight malaria. You are now as much at risk as someone who was born in the United States (a "non-immune" 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.

 

Symptoms and Diagnosis

What are the signs and symptoms of 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. 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 after being bitten by an infected mosquito?

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.

 

How do I know if I have malaria for sure?

Most people, at the beginning of the disease, have fever, sweats, chills, headaches, malaise, muscles aches, nausea and vomiting. Malaria can very rapidly become a severe and life-threatening disease. The surest way for you and your health-care provider to know whether you have malaria is to have a diagnostic test where a drop of your blood is examined under the microscope for the presence of malaria parasites. If you are sick and there is any suspicion of malaria (for example, if you have recently traveled in a malaria-risk area) the test should be performed without delay.

 

Preventing Malaria During Travel

I will be traveling outside of the US to an area with malaria; how do I find out what is the best drug to take against malaria?

 

Many effective antimalarial drugs are available. Your health care provider and you will decide on the best drug for you based on your travel plans, medical history, age, drug allergies, pregnancy status, and other health factors.

To allow enough time for the drugs to become effective and for a pharmacy to prepare any special doses of medicine (especially doses for children and infants), visit your health care provider 4-6 weeks before travel.

 

What is known about the long term effects of drugs that are commonly used to prevent and treat malaria?

In general, most drugs used to prevent and treat malaria have been shown to be well tolerated for at least 1 year or more.

 

Is it safe to buy my malaria drugs in the malaria-risk country where I will be traveling?

Buying medications abroad has its risks. The drugs could be of poor quality because of the way they are produced. The drugs could contain contaminants or they could be counterfeit drugs and therefore may not provide you the protection you need against malaria. In addition, some medications that are sold overseas are not used anymore in the United States or were never sold here. These drugs may not be safe or their safety has never been evaluated.

It would be best to purchase all the medications that you need before you leave the United States. As a precaution, note the name of the medication(s) and the name of the manufacturer(s). That way, in case of accidental loss, you can replace the drug(s) abroad at a reliable vendor.

 

Isn't there a malaria vaccine? And if not, why?

There is currently no malaria vaccine approved for human use. The malaria parasite is a complex organism with a complicated life cycle. Its antigens are constantly changing and developing a vaccine against these varying antigens is very difficult. In addition, scientists do not yet totally understand the complex immune responses that protect humans against malaria. However, many scientists all over the world are working on developing an effective vaccine. Because other methods of fighting malaria, including drugs, insecticides, and bed nets, have not succeeded in eliminating the disease, the search for a vaccine is considered to be one of the most important research projects in public health.

 

Malaria and Infants and Children

Should infants and children be given antimalarial drugs?

Yes, but not all types of malaria drugs. Children of any age can get malaria and any child traveling to a malaria-risk area should be on an antimalarial drug. However, some antimalarial drugs are not suitable for children. Doses are based on the child's weight. More details can be found on Preventing Malaria in Infants and Children.

Pregnancy, Preconception, and Breastfeeding

I am 4 months pregnant but want to visit a malaria-risk country for 2 weeks. Is it safe to do so?

CDC advises women who are pregnant or likely to become pregnant to not travel to areas with malaria risk, if possible. Malaria in pregnant women can be more severe than in women who are not pregnant. Malaria can increase the risk for serious pregnancy outcomes, including prematurity, miscarriage, and stillbirth. If travel to a malarious area cannot be postponed, use of an effective chemoprophylaxis regimen is essential. However, no preventive drugs are completely effective. Please consider these risks (and other health risks as well) and discuss them with your health-care provider.

 

I plan to become pregnant after I return from a malaria risk area. How long does it take it take for antimalarial drugs to clear the body?

Because there is no evidence that chloroquine and mefloquine are associated with congenital defects when used for preventing malaria (prophylaxis), CDC does not recommend that women planning pregnancy need to wait a specific period of time after their use before becoming pregnant. However, if women or their health-care providers wish to decrease the amount of antimalarial drug in the body before conception. After two, four, and six half-lives, approximately 25%, 6%, and 2% of the drug remain in the body.

 

Is it considered safe for me to breastfeed while taking an antimalarial drug?

There is limited data available about the safety of antimalarial drugs and breastfeeding. However, the amount of antimalarial drug transferred from the nursing mother to her infant is not thought to be harmful to the infant. Very small amounts of the antimalarial drugs chloroquine and mefloquine are excreted in the breast milk of women who are breastfeeding. Although there is limited information about the use of doxycycline in breastfeeding women, most experts consider it unlikely to cause any harm as well.

No information is available on the amount of primaquine that enters human breast milk; the mother and infant should be tested for G6PD deficiency before primaquine is given to a woman who is breastfeeding.

It is not known whether atovaquone, which is a component of the antimalarial drug Malarone, is excreted in human milk. Proguanil, the other component of Malarone, is excreted in human milk in small quantities.

Note: Because there is little information available on the safety of atovaquone/proguanil to prevent malaria in infants weighing less than 5 kg (11 lbs), CDC does not currently recommend it for the prevention of malaria in women breastfeeding infants weighing less than 5 kg.

 

If I am taking an antimalarial drug and breastfeeding, will my baby be protected from malaria because of the medication transferred in my breast milk?

No. Based on experience with other antimalarial drugs, the quantity of drug transferred in breast milk is not likely to be enough to provide protection against malaria for the infant.

Other Preventive Measures

I live in an area where malaria is a problem, how can I prevent myself and my family from getting sick?

You and your family can prevent malaria by:

  • Keeping mosquitoes from biting you, especially at night
  • Taking antimalarial drugs to kill the parasites
  • Spraying insecticides on your home's walls to kill adult mosquitoes that come inside
  • Sleeping under bed nets - especially effective if they have been treated with insecticide, and
  • Using insect repellent and wearing long-sleeved clothing if out of doors at night

 

After Returning from a Malaria Risk Area

How long after returning from an area with malaria could I develop malaria?

Any traveler who becomes ill with a fever or flu-like illness while traveling, and up to 1 year after returning home should immediately seek professional medical care. You should tell your healthcare provider that you have been traveling in a malaria-risk area.

Can I give blood if I have been in a country where there is malaria?

It depends on what areas of that country you visited, how long ago you were there, and whether you ever had malaria. In general, most travelers to an area with malaria are deferred from donating blood for 1 year after their return. People who used to live in malaria-risk areas cannot donate blood for 3 years. People diagnosed with malaria cannot donate blood for 3 years after treatment, during which time they must have remained free of symptoms of malaria.

Blood banks follow strict guidelines for accepting or deferring donors who have been in malaria-endemic areas. This is in order to avoid collecting blood for transfusions from an infected donor. In the United States during the period 1963-1999, there were 93 cases reported to CDC where people acquired malaria through a transfusion. Because of these control measures, transfusion-transmitted malaria is very rare in the United States and occurs at a rate of less than 1 per million units of blood transfused.

Treating Malaria

When should malaria be treated?

The disease should be treated early in its course, before it becomes serious and life-threatening. Several good antimalarial drugs are available, and should be taken early on. The most important step is to think about malaria if you are presently in, or have recently been in, an area with malaria, so that the disease is diagnosed and treated in time.

What is the treatment for malaria?

Malaria can be cured with prescription drugs. The type of drugs and length of treatment depend on the type of malaria, where the person was infected, their age, whether they are pregnant, and how sick they are at the start of treatment.

When is malaria self-treatment recommended?

Travelers who are taking effective malaria preventive drugs but who will be in very remote areas may decide, in consultation with their healthcare provider, to take along antimalarial mediation for self-treatment. Malaria self-treatment should begin right away if fever, chills, or other influenza-like illness occurs and if professional medical care is not available within 24 hours. Self-treatment of a possible malarial infection is only a temporary measure and immediate medical care is important.

The CDC Malaria Branch (Malaria Hotline 770-488-7788) can provide consultation to health-care providers on other potential options for self-treatment if atovaquone/proguanil cannot be used.

 

If I get malaria, will I have it for the rest of my life?

No, not necessarily. Malaria can be treated. If the right drugs are used, people who have malaria can be cured and all the malaria parasites can be cleared from their body. However, the disease can continue if it is not treated or if it is treated with the wrong drug. Some drugs are not effective because the parasite is resistant to them. Some people with malaria may be treated with the right drug, but at the wrong dose or for too short a period of time.

Two types (species) of parasites, Plasmodium vivax and P. ovale, have liver stages and can remain in the body for years without causing sickness. If not treated, these liver stages may re-activate and cause malaria attacks ("relapses") after months or years without symptoms. People diagnosed with P. vivax or P. ovale are often given a second drug to help prevent these relapses. Another type of malaria, P. malariae, if not treated, has been known to stay in the blood of some people for several decades.

However, in general, if you are correctly treated for malaria, the parasites are eliminated and you are no longer infected with malaria.

Where Malaria Occurs

Where does malaria occur?

Malaria typically is found in warmer regions of the world -- in tropical and subtropical countries. Higher temperatures allow the Anopheles mosquito to thrive. Malaria parasites, which grow and develop inside the mosquito, need warmth to complete their growth before they are mature enough to be transmitted to humans.

Malaria occurs in over 100 countries and territories. More than 40% of the world's population is at risk. Large areas of Central and South America, Hispaniola (the Caribbean island that is divided between Haiti and the Dominican Republic), Africa, South Asia, Southeast Asia, the Middle East, and Oceania are considered malaria-risk areas.

Yet malaria does not occur in all warm climates. For example, malaria has been eliminated in some countries with warm climates, while a few other countries have no malaria because Anopheles mosquitoes are not found there.

 

Why is malaria so common in Africa?

In Africa south of the Sahara, the principal malaria mosquito, Anopheles gambiae, transmits malaria very efficiently. The type of malaria parasite most often found, Plasmodium falciparum, causes severe, potentially fatal disease. Lack of resources and political instability can prevent the building of solid malaria control programs. In addition, malaria parasites are increasingly resistant to antimalarial drugs, presenting one more barrier to malaria control in that continent.

 

In some countries, malaria is said to exist in "rural" areas. How would one know if an area is rural vs urban?

What constitutes a rural area can vary by country. In general, urbanization can be said to involve both population size and economic development of an area in which there is concentrated commercial activity, such as manufacturing, the sale of goods and services, and transportation. Rural areas tend to have less commercial activity, less population density, more green space, and agriculture may be a main feature.

 

Which resorts in coastal malarious areas of Mexico are considered to have no known malaria risk?

Resorts which are located in malarious areas along the Pacific and Gulf Coasts of Mexico can vary from open-air to closed well-screened or air conditioned facilities. In general, a traveler staying in a screened or air conditioned accommodation is at lower risk for contracting malaria than a traveler staying in an open-air facility. Additionally, the risk for malaria infection can increase if the traveler ventures away from the immediate grounds of their resort to visit rural areas, especially between dusk and dawn.

 

Eradication

Wasn't malaria eradicated years ago?

No, not in all parts of the world. Malaria has been eradicated from many developed countries with temperate climates. However, the disease remains a major health problem in many developing countries, in tropical and subtropical parts of the world.

An eradication campaign was started in the 1950s, but it failed globally because of problems including the resistance of mosquitoes to insecticides used to kill them, the resistance of malaria parasites to drugs used to treat them, and administrative issues. In addition, the eradication campaign never involved most of Africa, where malaria is the most common.

Malaria in the United States

  • 1,337 cases of malaria, including 8 deaths, were reported for 2002 in the United States, even though malaria has been eradicated in this country since the early 1950's
  • Of the 1,337 malaria cases reported for 2002 in the United States, all but five were imported, i.e., acquired in malaria-endemic countries.
  • Between 1957 and 2003, in the United States, 63 outbreaks of locally transmitted mosquito-borne malaria have occurred; in such outbreaks, local mosquitoes become infected by biting persons carrying malaria parasites (acquired in endemic areas) and then transmit malaria to local residents.
  • Of the ten species of Anopheles mosquitoes found in the United States, the two species that were responsible for malaria transmission prior to eradication (Anopheles quadrimaculatus in the east and An. freeborni in the west) are still widely prevalent; thus there is a constant risk that malaria could be reintroduced in the United States.
  • During 1963-1999, 93 cases of transfusion-transmitted malaria were reported in the United States; approximately two thirds of these cases could have been prevented if the implicated donors had been deferred according to established guidelines.

Malaria Worldwide

  • Forty-one percent of the world's population live in areas where malaria is transmitted (e.g., parts of Africa, Asia, the Middle East, Central and South America, Hispaniola, and Oceania).
  • Each year 350–500 million cases of malaria occur worldwide, and over one million people die, most of them young children in sub-Saharan Africa.
  • In areas of Africa with high malaria transmission, an estimated 990,000 people died of malaria in 1995 – over 2700 deaths per day, or 2 deaths per minute.
  • In 2002, malaria was the fourth cause of death in children in developing countries, after perinatal conditions (conditions occurring around the time of birth), lower respiratory infections (pneumonias), and diarrheal diseases. Malaria caused 10.7% of all children's deaths in developing countries.
  • In Malawi in 2001, malaria accounted for 22% of all hospital admissions, 26% of all outpatient visits, and 28% of all hospital deaths. Not all people go to hospitals when sick or having a baby, and many die at home. Thus the true numbers of death and disease caused by malaria are likely much higher.

Biology, Pathology, Epidemiology

  • Residents of Asembo Bay (Western Kenya) were bitten 60-300 times a year by a malaria-carrying mosquito in the 1990's, before control measures (including the use of insecticide-treated bed nets) were put in place.
  • Among the four malaria species that infect humans, Plasmodium vivax and P. ovale can develop dormant liver stages that can reactivate after symptomless intervals of up to 2 (P. vivax) to 4 years (P. ovale).
  • 84% of the blood transfusions given in March-June 2000 in a major hospital in Kinshasa (Democratic Republic of Congo) were for anemia caused by malaria.
  • Pregnant women have increased susceptibility to Plasmodium falciparum malaria; in malaria-endemic countries, P. falciparum contributes to 8-14% of low birth weight, which in turn decreases the chance of a baby’s survival
  • After a single sporozoite (the parasite form inoculated by the female mosquito) of Plasmodium falciparum invades a liver cell, the parasite grows in 6 days and produces 30,000-40,000 daughter cells (merozoites) which are released into the blood when the liver cell ruptures. In the blood, after a single merozoite invades a red blood cell, the parasite grows in 48 hours and produces 8-24 daughter cells, which are released into the blood when the red blood cell ruptures.

Prevention and Treatment

  • Four Nobel prizes have been awarded for work associated with malaria, to Sir Ronald Ross (1902), Charles Louis Alphonse Laveran (1907), Julius Wagner-Jauregg (1927) and Paul Hermann Muller (1948).
  • Two important currently used antimalarial drugs are derived from plants whose medicinal values had been noted for centuries: artemisinin from the Qinghao plant (Artemisia annua L, China, 4th century) and quinine from the cinchona tree (South America, 17th century).
  • Insecticide-treated bed nets decreased the mortality of children aged 1-11 months in a trial in western Kenya in 1997-1999.
  • A survey in Southeast Asia in 1999-2000 showed that of 104 shop-bought samples purportedly containing the antimalarial drug artesunate, 38% contained no artesunate.
  • The average cost for potentially life-saving treatments of malaria are estimated to be US$0.13 for chloroquine, US$0.14 for sulfadoxine-pyrimethamine, and US$2.68 for a 7-day course of quinine.

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Credit:CDC,WHO,UN,Oxford University