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The Disease
What is malaria?
Malaria is a serious and sometimes
fatal disease caused by a parasite. Patients with malaria typically
are 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 any of the malaria species can make a person feel very
ill; infection with P. falciparum, if not promptly treated,
may be fatal. Although malaria can be a fatal disease, illness and death
from malaria are largely preventable.
Is malaria a common disease?
The World Health Organization
estimates that each year 300-500 million cases of malaria occur and
that more than 1 million people die of malaria. About 1,200 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 the Indian
subcontinent.
Is malaria a serious disease?
Malaria is a leading
cause of death and disease worldwide, 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.
Wasn’t malaria eradicated years ago?
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 due to 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.
If I live in the United States, can I still get malaria?
Malaria
was eradicated from the United States in the early 1950s. However, malaria
is common in many developing countries and travelers who visit these
areas risk getting malaria.
Returning travelers and arriving immigrants could also reintroduce
the disease in the United States if they are infected with malaria when
they return. The mosquito that transmits malaria, Anopheles,
is found throughout much of the United States. If local mosquitoes bite
an infected person, those mosquitoes can, in turn, infect local residents
( introduced 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 (Haiti and the Dominican Republic), Africa,
the Indian subcontinent, Southeast Asia, the Middle East, and Oceania
are considered malaria-risk areas.
Yet malaria does not occur in all
warm climates. For example, economic development and public health
efforts have eliminated malaria from the southern United States, southern
Europe, Taiwan, Singapore, and all of the Caribbean
islands (except Hispaniola). Some Pacific islands 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. Economic problems 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.
How People Get Malaria (Transmission)
How is malaria transmitted?
Usually, people get malaria
by being bitten by an infected female Anopheles mosquito.
Only Anopheles mosquitoes can transmit malaria and they must
have been infected by a previous blood meal taken on an infected person.
When a mosquito bites, a small amount of blood is taken in which contains
the microscopic malaria parasites. The parasite grows and matures in
the mosquito’s gut for a week or more, then travels to the mosquito’s
salivary glands. When the mosquito next takes a blood meal, these parasites
mix with the saliva and are injected into the bite.
Once in the blood, the parasites travel to the liver and enter liver
cells to grow and multiply. During this ‘incubation period’,
the infected person has no symptoms. After as few as 8 days or as long
as several months, the parasites leave the liver cells and enter red
blood cells. Once in the cells, they continue to grow and multiply.
After they mature, the infected red blood cells rupture, freeing the
parasites to attack and enter other red blood cells. Toxins released
when the red cells burst are what cause the typical fever, chills, and
flu-like malaria symptoms.
If a mosquito bites this infected person and ingests certain types
of malaria parasites ("gametocytes"), the cycle of transmission
continues.
Because the malaria parasite is found in red blood cells, 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 fetus before or during
delivery (‘congenital’ malaria).
Malaria is not transmitted from person to person like a cold or the flu. You
cannot get malaria from casual contact with malaria-infected people.
I live in the United States, where there is no malaria. Can
I still get malaria?
You will be most at risk if you travel
to countries where malaria is endemic (‘malaria-risk
areas’). However, a few cases of malaria occur every year
in the United States in people who have not left the country. Fortunately,
these are very rare occurrences. Malaria may be transmitted through
blood transfusions or by local transmission (see introduced malaria above).
A few cases of congenital malaria are reported each year;
infected mothers pass the parasite to their fetus during pregnancy or
delivery. Malaria remains a public health concern in the United States
even though the disease has been eradicated in this country.
Who Is at Risk
Who is at risk for malaria?
Anyone can get malaria. Most cases occur in residents of countries
with malaria transmission and travelers to those countries. In
non-endemic countries, cases can occur in non-travelers as congenital malaria,
introduced malaria, or transfusion malaria (see above).
Who are
the people most at risk of severe and fatal malaria?
Plasmodium
falciparum causes severe and life-threatening
malaria; this parasite is very common in many countries in
Africa south of the Sahara. 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 severely
ill and die. Poor people living in rural areas who lack knowledge,
money, or access to health care are more vulnerable to the 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.
Preventing Malaria
If 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
- destroying places around your home where mosquitoes breed
- 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
- wearing insect repellent and long-sleeved clothing if out of
doors at night
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.
Traveling and Malaria
I will be traveling outside of the United States. What should
I do to avoid getting malaria or other infectious diseases?
Some
simple precautions will help protect your health while traveling.
CDC’s Travelers’ Health provides
detailed information on malaria risk by country, prevention information
including recommended antimalarial drugs, and vaccination recommendations
for other diseases.
Travelers leaving the United States should:
- Visit your health care provider 4-6 weeks before foreign travel
for any necessary vaccinations and a prescription for an antimalarial
drug, if needed.
- Take your antimalarial drug exactly on schedule without missing
doses.
- Wear insect repellent to prevent mosquito and other insect bites.
Your insect repellent should contain DEET as its active ingredient.
To prevent malaria, wear insect repellent if out of doors between
dusk and dawn when the mosquito that transmits malaria is biting.
- Wear long pants and long-sleeved clothing.
- Sleep under a mosquito bed net that has been dipped in permethrin
insecticide if you are not living in screened or air-conditioned
housing.
Should I buy my malaria pills in the malaria-risk country where
I will be traveling?
Buying medications abroad has its risks.
The drugs could be of substandard quality because of poor manufacturing
practices. The drugs could contain contaminants or they could be counterfeit drugs.
Such products 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.
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. Former residents of
malaria-risk areas will be deferred for 3 years. Persons 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 (e.g.
American
Red Cross) for accepting or deferring donors who have been
in malaria-endemic areas. This is in order to avoid collecting blood
from an infected donor and inadvertently transmitting malaria to
the recipient. 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.
I was born 40 years ago in a malaria-endemic country and immigrated
to the United States 10 years ago. When I was a child I had some
malaria, but as I grew older malaria bothered me less and less. I
guess that I just became immune. Now I am planning to go back to
my native country for two months to visit friends and relatives.
Do I really need to worry about getting malaria?
Yes, anyone
who goes to a malaria-risk country should take precautions against
acquiring malaria. During the last ten years that you have spent
in the United States, you have lost any malaria immunity that you
might have acquired while living in your native country. Without
frequent exposure to malaria parasites, the immune system of your
body has forgotten how 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.
I am 4 months pregnant but want to visit a malaria-risk country
for 2 weeks. Should I do that?
CDC advises women who are
pregnant or likely to become pregnant to avoid travel to areas with
malaria risk, if possible. Malaria
in pregnant women can be more severe than in nonpregnant women.
Malaria can increase the risk for adverse pregnancy outcomes, including
prematurity, miscarriage, and stillbirth. No preventive drugs are completely
effective. Please consider these risks (and other health risks as well)
and discuss with your health-care provider.
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 up to 1 year later.
Two kinds of malaria, P. vivax and P. ovale, can
relapse. 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?
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 order 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.
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 health care
provider that you have been traveling in a malaria-risk area.
Treating Malaria
When should malaria be treated?
The disease should be treated early in its course, before it becomes severe and poses a risk to the patient's life. Several good antimalarial drugs are available, and should be administered early on. The most important step is to think about 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 which kind of malaria
is diagnosed, where the patient was infected, the age of the patient,
and how severely ill the patient is at start of treatment.
If I get malaria, will I have it for the rest of my life?
Malaria
can be treated. If the right drugs are used, people who have malaria
can be cured and all their malaria parasites can be eliminated. However,
the disease can persist if it is left untreated or if it is treated
with the wrong drug. Some drugs are ineffective because the parasite
is resistant. Some patients 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 dormant liver stages that can remain silent for
years. Left untreated, these liver stages may reactivate and cause
malaria attacks ("relapses") after months or years without
symptoms. Patients diagnosed with vivax or ovale are
often given a second drug to help prevent these relapses. Another
type (species), P. malariae, if left untreated, has been
known to persist in the blood of some persons for several decades.
But in general, if you are correctly treated for malaria, the parasites
are eliminated and you are no longer infected with malaria.
Malaria Drugs
How do I find out what is the best drug to take against malaria?
Regional
Malaria Information gives 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 your drug based on your travel itinerary, your
medical history, your age, drug allergies, pregnancy, and other health
factors.
To allow sufficient 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.
Can children also take malaria pills?
Children of any
age can get malaria and any child traveling to a malaria-risk area should
be on an antimalarial drug. Doses are based on the child’s
weight. More details on Preventing
Malaria in Infants and Children.
Date: August
13,
2004
Content source: National Center for Infectious Diseases, Division of Parasitic Diseases
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