K4A - About malaria
- Malaria is a life-threatening disease caused by
parasites that are transmitted to people
through the bites of infected mosquitoes.
- In 2008, malaria caused nearly one million
deaths, mostly among African children.
- Malaria is preventable and curable.
- Malaria can decrease gross domestic product by
as much as 1.3% in countries with high disease rates.
- Non-immune travelers from malaria-free areas are
very vulnerable to the disease when they get
In 2008, there were 247 million cases of malaria and
nearly one million deaths – mostly among children living
in Africa. In Africa a child dies every 45 seconds of
Malaria, the disease accounts for 20% of all childhood
Malaria is caused by Plasmodium parasites. The
parasites are spread to people through the bites of
infected Anopheles mosquitoes, called "malaria vectors",
which bite mainly between dusk and dawn.
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.
In recent years, some human cases of malaria have also
occurred with Plasmodium knowlesi – a monkey malaria
that occurs in certain forested areas of South-East Asia.
Malaria is transmitted exclusively through the bites of
Anopheles mosquitoes. The intensity of transmission
depends on factors related to the parasite, the vector,
the human host, and the environment.
About 20 different Anopheles species are locally
important around the world. All of the important vector
species bite at night. They breed in shallow collections
of freshwater like puddles, ricefields, and hoofprints.
Transmission is more intense in places where the
mosquito is relatively long-lived (so that the parasite
has time to complete its development inside the mosquito)
and where it prefers to bite humans rather than other
animals. For example, the long lifespan and strong
human-biting habit of the African vector species is the
underlying reason why more than 85% of the world's
malaria deaths are in Africa.
Human immunity is another important factor, especially
among adults in areas of moderate or intense
transmission conditions. Immunity is developed over
years of exposure, and while it never gives complete
protection, it does reduce the risk that malaria
infection will cause severe disease. For this reason,
most malaria deaths in Africa occur in young children,
whereas in areas with less transmission and low immunity,
all age groups are at risk.
Transmission also depends on climatic conditions that
may affect the abundance and survival of mosquitoes,
such as rainfall patterns, temperature and humidity. In
many places, transmission is seasonal, with the peak
during and just after the rainy season. Malaria
epidemics can occur when climate and other conditions
suddenly favour transmission in areas where people have
little or no immunity to malaria. They can also occur
when people with low immunity move into areas with
intense malaria transmission, for instance to find work,
or as refugees.
Malaria is an acute febrile illness. Symptoms appear
seven days or more (usually 10–15 days) after the
infective mosquito bite. The first symptoms – fever,
headache, chills and vomiting – may be mild and
difficult to recognize as malaria. If not treated within
24 hours, P. falciparum malaria can progress to severe
illness often leading to death. Children in endemic
areas with severe disease frequently develop one or more
of the following syndromic presentations: severe anaemia,
respiratory distress in relation to metabolic acidosis,
or cerebral malaria. In adults,
multi-organ involvement is also frequent.
For both P. vivax and P. ovale, clinical relapses may
occur weeks to months after the first infection, even if
the patient has left the malarious area. These new
episodes arise from "dormant" liver forms (absent in P.
Falciparum and P.malariae), and special treatment –
targeted at these liver stages – is mandatory for a
Who is at risk?
Approximately half of the world's population is at risk
of malaria. Most malaria cases and deaths occur in
sub-Saharan Africa. However, Asia, Latin America, and to
a lesser extent the Middle East and parts of Europe are
also affected. In 2008, malaria was present in 108
countries and territories.
Specific population risk groups include:
- Young children in stable transmission areas who
have not yet developed protective immunity against
the most severe forms of the disease. Young children
contribute the bulk of malaria deaths worldwide.
- Non-immune pregnant women are at risk as malaria
causes high rates of miscarriage (up to 60% in P.
falciparum infection) and maternal death rates of
- Semi-immune pregnant women in areas of high
transmission. Malaria can result in miscarriage and
low birth weight, especially during the first and
second pregnancies. An estimated 200 000 infants die
annually as a result of malaria infection during
- Semi-immune HIV-infected pregnant women in
stable transmission areas are at increased risk of
malaria during all pregnancies. Women with malaria
infection of the placenta also have a higher risk of
passing HIV infection to their newborns.
- People with HIV/AIDS are at increased risk of
malaria disease when infected.
- International travellers from non-endemic areas
are at high risk of malaria and its consequences
because they lack immunity.
- Immigrants from endemic areas and their children
living in non-endemic areas and returning to their
home countries to visit friends and relatives are
similarly at risk because of waning or absent
Diagnosis and treatment
Early diagnosis and treatment of malaria reduces disease
and prevents deaths. It also contributes to reducing
malaria transmission. The best available treatment,
particularly for P. falciparum malaria, is
artemisinin-based combination therapy (ACT).
World Health Organisation recommends that malaria be
confirmed by parasite-based diagnosis before giving
treatment. Results of parasitological confirmation can
be available in a few minutes. Treatment solely on the
basis of symptoms should only be considered when a
parasitological diagnosis is not possible.
Growing resistance to antimalarial medicines has spread
very rapidly, undermining malaria control efforts. When
treated with an artemisinin-based monotherapy, patients
may discontinue treatment early following the rapid
clearance of malaria symptoms. This results in partial
treatment and patients still have persistent parasites
in their blood. Without a second drug given as part of a
combination (as is done with an ACT), these resistant
parasites survive and can be passed on to a
mosquito and then another person. Monotherapies are
therefore the primary force behind the spread of
If resistance to artemisinins develops and spreads to
other large geographical areas, as has happened before
with chloroquine and sulfacoxine-pyrimethamine (SP), the
public health consequences could be dire, as no
alternative antimalarial medicines will be available in
the near future.
World Health Organisation recommends the routine
monitoring of antimalarial drug resistance, and supports
countries to strengthen their efforts in this important
area of work.
Vector control is the primary public health intervention
for reducing malaria transmission at the community
level. It is the only intervention that can reduce
malaria transmission from very high levels to close to
zero. In high transmission areas, it can reduce child
mortality rates and the prevalence of severe anaemia.
For individuals personal protection against mosquito
bites represents the first line of defence for malaria
Two forms of vector control are effective in a wide
range of circumstances. These are:
- insecticide-treated mosquito nets (ITNs): Long
lasting insecticide impregnated nets (LLINs) are the
preferred form of insecticide treated nets for
public health distribution programmes. WHO
recommends universal vector control coverage, and in
most places, the most cost effective way to achieve
this is through provision of LLINs, so that everyone
in high transmission areas sleeps under a LLIN every
- indoor spraying with residual insecticides:
Indoor residual spraying (IRS) with insecticides is
the most powerful way to rapidly reduce malaria
transmission. Its full potential is realized when at
least 80% of houses in targeted areas are sprayed.
Indoor spraying is effective for 3–6 months,
depending on the insecticide used and the type of
surface on which it is sprayed. DDT can be effective
for 9–12 months in some cases. Longer-lasting forms
of IRS insecticides are under development.
Drugs can also be used to prevent malaria. For
travellers, malaria can be prevented through
chemoprophylaxis, which suppresses the blood stage of
malaria infections, thereby preventing malaria disease.
Mosquito control is being strengthened in many areas,
but there are significant challenges, including:
- an increasing mosquito resistance to
insecticides, including DDT and pyrethroids,
particularly in Africa; and
- a lack of alternative, cost-effective and safe
The development of new, alternative insecticides is
an expensive and long-term endeavour. Detection of
insecticide resistance should be an essential component
of all national malaria control efforts to ensure that
the most effective vector control methods are being used.
The choice of insecticide for IRS is a decision that
should always be informed by local and recent data on
the susceptibility of the target vectors, and ensuring
the availability of such data is a shared responsibility.
Malaria causes significant economic losses, and can
decrease gross domestic product (GDP) by as much as 1.3%
in countries with high levels of transmission. Over the
long term, these aggregated annual losses have resulted
in substantial differences in GDP between countries with
and without malaria, particularly in Africa. The health
costs of malaria include both personal and public
expenditures on prevention and treatment. In some
heavy-burden countries, the disease accounts for:
- up to 40% of public health expenditures;
- 30% to 50% of inpatient hospital admissions;
- up to 60% of outpatient health clinic visits.
Malaria disproportionately affects poor people who
cannot afford treatment or have limited access to health
care, trapping families and communities in a downward
spiral of poverty.
Historically, many countries – especially in temperate
and sub-tropical zones – have been successful in
eliminating malaria. The global malaria eradication
campaign, launched by WHO in 1955, was successful in
eliminating the disease in some countries, but
ultimately failed to achieve its overall goal, thus
being abandoned less than two decades later in favour of
the less ambitious goal of malaria control. In recent
years, however, interest in malaria eradication has
Large-scale use of World Health Organisation-recommended
strategies, currently available tools, strong national
commitments, and coordinated efforts with partners, will
enable more countries – particularly those where malaria
transmission is low and unstable – to progress towards