Malaria
What is Malaria?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. 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.
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.![]() Several groups of mosquitoes are medically important. This mosquito, which belongs to the genus Anopheles, transmits the malaria parasite. Note the long palpi—they are about as long as the proboscis. 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 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.
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.
Uncomplicated MalariaThe classical (but rarely observed) malaria attack lasts 6-10 hours. It consists of:
Classically (but infrequently observed) the attacks occur every second day with the "tertian" parasites (P. falciparum, P. vivax, and P. ovale) and every third day with the "quartan" parasite (P. malariae). More commonly, the patient presents with a combination of the following symptoms:
In countries where cases of malaria are infrequent, these symptoms may be attributed to influenza, a cold, or other common infections, especially if malaria is not suspected. Conversely, in countries where malaria is frequent, residents often recognize the symptoms as malaria and treat themselves without seeking diagnostic confirmation ("presumptive treatment"). Physical findings may include:
In P. falciparum malaria, additional findings may include:
Diagnosis of malaria depends on the demonstration of parasites on a blood smear examined under a microscope. In P. falciparum malaria, additional laboratory findings may include mild anemia, mild decrease in blood platelets (thrombocytopenia), elevation of bilirubin, elevation of aminotransferases, albuminuria, and the presence of abnormal bodies in the urine (urinary "casts").
Severe MalariaSevere malaria occurs when P. falciparum infections are complicated by serious organ failures or abnormalities in the patient's blood or metabolism. The manifestations of severe malaria include:
Other manifestations that should raise concern are:
Severe malaria occurs most often in persons who have no immunity to malaria or whose immunity has decreased. These include all residents of areas with low or no malaria transmission, and young children and pregnant women in areas with high transmission. In all areas, severe malaria is a medical emergency and should be treated urgently and aggressively.
Malaria RelapsesIn P. vivax and P. ovale infections, patients having recovered from the first episode of illness may suffer several additional attacks ("relapses") after months or even years without symptoms. Relapses occur because P. vivax and P. ovale have dormant liver stage parasites ("hypnozoites") that may reactivate. Treatment to reduce the chance of such relapses is available and should follow treatment of the first attack.
Other Manifestations of Malaria
How soon will a person feel sick after being bitten by an infected mosquito?Following the infective bite by the Anopheles mosquito, a period of time (the "incubation period") goes by before the first symptoms appear. The incubation period in most cases varies from 7 to 30 days. The shorter periods are observed most frequently with P. falciparum and the longer ones with P. malariae. 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.Antimalarial drugs taken for prophylaxis by travelers can delay the appearance of malaria symptoms by weeks or months, long after the traveler has left the malaria-endemic area. (This can happen particularly with P. vivax and P. ovale, both of which can produce dormant liver stage parasites; the liver stages may reactivate and cause disease months after the infective mosquito bite.) Such long delays between exposure and development of symptoms can result in misdiagnosis or delayed diagnosis because of reduced clinical suspicion by the health-care provider. Returned travelers should always remind their health-care providers of any travel in malaria-risk areas during the past 12 months.
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.Diagnosis of malaria can be difficult:
Malaria parasites can be identified by examining under the microscope a drop of the patient's blood, spread out as a "blood smear" on a microscope slide. Prior to examination, the specimen is stained (most often with the Giemsa stain) to give to the parasites a distinctive appearance. This technique remains the gold standard for laboratory confirmation of malaria. However, it depends on the quality of the reagents, of the microscope, and on the experience of the laboratorian.
Another diagnostic approach: Parasite nucleic acids are detected using polymerase chain reaction (PCR). This technique is more accurate than microscopy. However, it is expensive, and requires a specialized laboratory (even though technical advances will likely result in field-operated PCR machines). Serology detects antibodies against malaria parasites, using either indirect immunofluorescence (IFA) or enzyme-linked immunosorbent assay (ELISA). Serology does not detect current infection but rather measures past experience.
What is the best drug to take against malaria?CDC Travelers' Health destination pages give detailed information on the proper drugs to take for the area you are visiting and specific prevention tips.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. 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.
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. See also Traveling Safely with Infants and Children.
Pregnancy and MalariaCDC 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.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, this table provides information on the half-lives of selected antimalarial drugs. 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. 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.
In an area where malaria is a problem, you can prevent malaria by:
How long after returning from an area with malaria could you 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.
When and how 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.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. 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.
Malaria FactsMalaria in the United States
Malaria Worldwide
Biology, Pathology, Epidemiology
Prevention and Treatment
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