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.
