Chapter 1: The burden of malaria in Africa

1. The burden of malaria
in Africa
About 90% of all malaria deaths in the world
today occur in Africa south of the Sahara.
This is because the majority of infections inAfrica are caused by Plasmodium falciparum,
the most dangerous of the four humanmalaria parasites. It is also because the mosteffective malaria vector – the mosquito
Anopheles gambiae – is the most widespreadin Africa and the most difficult to control. An
estimated one million people in Africa die
from malaria each year and most of these arechildren under 5 years old (1).
Malaria affects the lives of almost all
people living in the area of Africa defined by
the southern fringes of the Sahara Desert
in the north, and a latitude of about 28°
in the south. Most people at risk of thedisease live in areas of relatively stablemalaria transmission – infection is commonand occurs with sufficient frequency thatsome level of immunity develops. A smaller
proportion of people live in areas whererisk of malaria is more seasonal and lesspredictable, because of either altitude or
rainfall patterns. People living in theperipheral areas north or south of themain endemic area (Figure 1.1) orbordering highland areas are vulnerable
to highly seasonal transmission andto malaria epidemics.

Jamahiriya, Morocco, and Tunisia. In thesecountries the disease was caused
predominantly by Plasmodium vivax andtransmitted by mosquitoes that were mucheasier to control than those in Africa southof the Sahara. Surveillance efforts continue
in most of these countries in order to prevent
both a reintroduction of malaria parasites tolocal mosquito populations, and theintroduction of other mosquito species that
could transmit malaria more efficiently (aparticular risk in southern Egypt). The malaria
situation in these countries is not consideredfurther in this report.
Malaria is endemic in some of the offshoreislands to the west of mainland Africa – Sao
Tome and Principe and São Tiago Island ofCape Verde. In the east, malaria is endemic in
Madagascar, in the Comoro islands (both theIslamic Federal Republic of the Comoros andthe French Territorial Collectivity of Mayotte),

The global targetof Roll Back Malariais to halve
malaria-associatedmorbidity andmortality by 2010
compared with levels
in year 2000.

Distribution of endemic malaria

In areas of stable malaria transmission, very
young children and pregnant women are thepopulation groups at highest risk for malaria
morbidity and mortality. Most children
experience their first malaria infections
during the first year or two of life, when they
have not yet acquired adequate clinicalimmunity – which makes these early years
particularly dangerous. Ninety percent of all
malaria deaths in Africa occur in young
children. Adult women in areas of stabletransmission have a high level of immunity,
but this is impaired especially in the firstpregnancy, with the result that risk ofinfection increases.
Malaria has been well controlled oreliminated in the five northernmost Africancountries, Algeria, Egypt, Libyan Arab

Roll Back
Malaria target

Endemic malaria
Malaria marginal/
epidemic prone

Source: reference 2
Figure 1.1

17

The Africa Malaria Report–2003

Malaria kills children inthree different ways
Infection inpregnancy

Acute febrileillness

Chronic,
repeated
infection

Low birth weightPreterm delivery

Cerebral malaria
Respiratory distressHypoglycaemia

Severeanaemia

and on Pemba and Zanzibar, but has been
eliminated from the island of Reunion. InMauritius, malaria has been well controlled
since the 1950s, but occasional outbreaks ofvivax malaria occur, the last in association
with a cyclone in 1982. Since that year
there has been a steady decrease in cases
and risk is now extremely low. Seychelles
has been free of malaria since 1930,
and malaria vectors are believed to
no longer exist there.

1.1

Burden of malaria on
health in Africa
Mortality

Death
Figure 1.2

Most of the malaria burden isfrom deaths in young children
Deaths (thousands)

1000

Rest of the world

Africa

800
600
400
200
00–4

5–14
Age (years)

15+

Although adults also become infected with malaria,
the illness is usually less severe thanks to theiracquired immunity. Infections in young children
are serious and may kill if not treated promptly.
Source: WHO Global Burden of Disease project, estimates for 2000,
reference 17
Figure 1.3

18

There are three principal ways in whichmalaria can contribute to death in young
children (Figure 1.2). First, an overwhelming
acute infection, which frequently presents as
seizures or coma (cerebral malaria), may kill achild directly and quickly. Second, repeatedmalaria infections contribute to thedevelopment of severe anaemia, which
substantially increases the risk of death.
Third, low birth weight – frequently theconsequence of malaria infection inpregnant women – is the major risk
factor for death in the first month oflife (3). In addition, repeated malaria
infections make young children more
susceptible to other common childhood
illnesses, such as diarrhoea and respiratory
infections, and thus contribute indirectly
to mortality (4).
The consensus view of recent studies andreviews is that malaria causes at least 20% of
all deaths in children under 5 years of age in
Africa (Figures 1.3 and 1.4). Althoughrespiratory disease caused by a variety of
infectious agents results in a similar
proportion of deaths, P. falciparum is themost important single infectious agent
causing death among young children.
Morbidity and long-term disabilityChildren who survive malaria may suffer
long-term consequences of the infection.
Repeated episodes of fever and illness
reduce appetite and restrict play, social
interaction, and educational opportunities,
thereby contributing to poor development.
An estimated 2% of children who recoverChapter 1: The burden of malaria in Africa

from malaria infections affecting thebrain (cerebral malaria) suffer from learning
impairments and disabilities due to brain
damage, including epilepsy and spasticity (5).

Under-five all cause mortality

1.2

Burden of malaria on African
health systems
In all malaria-endemic countries inAfrica, 25–40% (average 30%) of all
outpatient clinic visits are for malaria (withmost diagnosis made clinically). In thesesame countries, between 20% and 50% of all
hospital admissions are a consequence ofmalaria (see country profiles for details).
With high case-fatality rates due to latepresentation, inadequate management,
and unavailability or stock-outs of effective
drugs, malaria is also a major contributor
to deaths among hospital inpatients(Figure 1.5).
This high burden may in fact be partly a
result of misdiagnoses, since many facilities
lack laboratory capacity and it is often
difficult clinically to distinguish malaria fromother infectious diseases. Nonetheless, malaria
is responsible for a high proportion of publichealth expenditure on curative treatment, andsubstantial reductions in malaria incidence
would free up available health resources andfacilities and health workers’ time, to tackle
other health problems.

Per 1000 children under-five
19–79
80–126
127–165
166–211
212–316
No data

Source: UNICEF, State of the World's Children, 2003

Figure 1.4

Malaria burden on health facilities
Under-five50All ages

% of outpatient visits due to malaria

4030201.3100
Western Africa

Burden of malaria on the poor
Poor people are at increased risk both ofbecoming infected with malaria and ofbecoming infected more frequently. Childmortality rates are known to be higher inpoorer households and malaria is responsible
for a substantial proportion of these deaths.
In a demographic surveillance system inrural areas of the United Republic of Tanzania,
under-5 mortality following acute fever(much of which would be expected
to be due to malaria) was 39% higher in thepoorest socioeconomic group than inthe richest (6).
A survey in Zambia also found a
substantially higher prevalence of malaria
infection among the poorest population

50Central/Eastern Africa

Southern Africa% of hospital admissions due to malaria

403020100
Western Africa
50Central/Eastern Africa

Southern Africa% of hospital deaths due to malaria

403020100
Western Africa

Source:Figure 1.5

Central/Eastern Africa

Southern Africa

AFRO routine Health Information System data.
Averages 1998–2001.
Error bars give the standard errors.

19The Africa Malaria Report – 2003

Parasite prevalence is higher in poor children% under-fives infected

80

The prevalence ofmalaria infection
was higher inunder-fives frompoorer families
in 10 districts
suveyed in Zambia.

6040200
PoorestSecondMiddle

FourthRichest

Wealth quintile
Source: reference 7

Figure 1.6

groups (7) (Figure 1.6). Poor families live indwellings that offer little protection against
mosquitoes and are less able to afford
insecticide-treated nets. Poor people are alsoless likely to be able to pay either for
effective malaria treatment or fortransportation to a health facility capable oftreating the disease.
Both direct and indirect costs associatedwith a malaria episode represent a substantial
burden on the poorer households. A study innorthern Ghana found that, while the cost ofmalaria care was just 1% of the incomeof the rich, it was 34% of the income ofpoor households (8).

1.4

Recent trends inthe burden of malaria
Routine case detection and reporting
Data from health facilities are potentially
useful for monitoring time trends in thenumber of malaria cases and deaths but havesevere limitations (Figure 1.7). In Africa, mostcases of malaria are diagnosed on the basisof clinical symptoms and treatment ispresumptive, rather than based on laboratory
confirmation. Moreover, malaria parasitaemia
is common among clinic attendees in many
endemic areas, so that a positive laboratory
result does not necessarily mean that thepatient is ill with malaria. The main clinicalsymptoms of malaria – fever and general

20

weakness – are nonspecific and may well be
due to other common infections.
Reporting from facilities to districts andfrom districts to the ministry of health varies
in its completeness and timeliness fromcountry to country and often does notinclude nongovernment facilities. Thus,
routine reports of the number of malaria
cases and deaths have limited value forcomparisons of the malaria burden between
countries. Demographic and health surveys(DHS) and other sources (9) indicate that lessthan 40% of malaria morbidity and mortality
is seen in formal health facilities – a small
fraction of the total burden. However,routinely collected data are often the only
information available over a prolonged period
and over a wide geographical area. Whilethese data are of use for local programme
planning, major investment in improving boththe quality of health information systems andaccess to health services would be required
before their utility for monitoring changes inmalaria disease trends could be assessed.
At present, the most reliable data available
on trends in malaria deaths in children under
5 years of age is obtained from demographic
surveillance systems (DSS), which measure
deaths and possible causes prospectively overtime in populations of known size andcomposition. The number of DSS sites isincreasing: 24 sites in 13 African countries
are collaborating under the INDEPTH network(International Network of field sites withcontinuous Demographic Evaluation ofChapter 1: The burden of malaria in Africa

Populations and Their Health) (10). Most ofthese sites are in eastern and southern Africa;
there are a few sites in the west of thecontinent but none in central Africa.

Trends in outpatient visits andhospital admissions for malaria

Recently, data from 1982–1998 wereanalysed across 28 DSS sites, adjusting forthe specificity and sensitivity of verbal
autopsies that were used to attribute deaths
to malaria (11). Malaria mortality in under-5s
almost doubled in eastern and southern
Africa over the period 1990–1998 comparedwith 1982–1989. It is known that theprevalence of malaria infections caused bychloroquine-resistant parasites increased
substantially from the late 1980s in thesesame areas (Figure 1.8). Thus, although themethodology cannot prove cause and effect,
it is very likely that some of this increase inchild mortality was related to some extent tothe spread of chloroquine-resistant malaria.
In west Africa the mortality rate remained
the same; here too, however, malaria became
proportionally more important (11). Analysis
of mortality data being collected fromINDEPTH using standardized verbal autopsy
questionnaires since 2000 should soon
provide further insight into more recent
disease trends.

80% outpatient visits due to malaria

60402001985

8019901995

2000% hospital admissions due to malaria

60
40200

Throughout Africa south of the Sahara, thedecrease in all-cause under-5 mortality that
was apparent during the 1970s and 1980s
levelled off in the 1990s (Figure 1.9), perhaps
partially as a result of increased malaria
mortality. Some of the important factors that
may have contributed to the increasing malaria
burden in these African settings include:

1985

1990

MalawiUR Tanzania

1995

2000

UgandaZambiaSource: Routine health information system data,
AFRO, for under-fives■ drug resistance (12)Figure 1.7

Malaria mortality in DSS sites
40

12% under-five deaths
due to malaria

Malaria mortality/1000
under-5 years

Estimates for average prevalences of Plasmodium falciparum of 63% in western Africa and 39% in easternand southern Africa, adjusted for variations in the sensitivity and specificity of verbal autopsy.

8403020
100

Western Africa

Eastern/southern Africa

1982–1989

Western Africa

1990–1998

Eastern/southern Africa

Source: reference 11

Figure 1.8

21The Africa Malaria Report – 2003

Trends in all-cause, under-five mortality in Africa

Deaths per 1000 under-fives

400

300

200

10001960

1980

1970

WesternEastern

1990

1995

Southern2000
Central
Source: DHS

Figure 1.9■ more frequent exposure of non-immune
populations■ emergence of HIV/AIDS (13, 14)■ climate and environmental change (15)of drug effectiveness. Coverage levels
approaching the Abuja target of 60% willprobably be required before the full effect ofITNs and effective treatment on child healthwill become apparent.

■ breakdown of control programmes (16).
References

1.5

Future prospects
From the time trends shown, it appears that
RBM is acting against a background ofincreasing malaria burden. With the typical
2–3-year delay in national-level data
becoming available, it is still too early toevaluate the extent to which RBM has
achieved a levelling-off or reversal of therising trend in the malaria burden. The very
low level of coverage with ITNs and untreatednets documented in 2000 and 2001 falls far
below the coverage levels in the ITN trials
that demonstrated substantial healthbenefits. It should therefore come as no
surprise that significant reductions in childmortality have yet to be observed. The impactof treatment coverage levels is more difficult
to estimate, given both a lack of information
on promptness and dosage, and varying levels

22

1. The World Health Report 2002: reducing risks,
promoting healthy life. Geneva, World HealthOrganization, 2002.
2. MARA/ARMA collaboration (Mapping Malaria Risk inAfrica), July 2002. www.mara.org.za.
3. Steketee RW et al. The burden of malaria in pregnancy
in malaria-endemic areas. American Journal of Tropical
Medicine and Hygiene, 2001, 64(1,2 S):28–35.
4. Molineaux L. Malaria and mortality: someepidemiological considerations. Annals of Tropical
Medicine and Parasitology, 1997, 91(7):811–825.
5. Murphy SC, Breman JG. Gaps in the childhood malaria
burden in Africa: cerebral malaria, neurological sequelae,
anemia, respiratory distress, hypoglycemia, andcomplications of pregnancy. American Journal of Tropical
Medicine and Hygiene, 2001, 64(1,2 S):57–67.
6. Mwageni E et al. Household wealth ranking and risksof malaria mortality in rural Tanzania. In: Third MIM
Pan-African Conference on Malaria, Arusha, Tanzania,
17–22 November 2002. Bethesda, MD, Multilateral
Initiative on Malaria: abstract 12.

Chapter 1: The burden of malaria in Africa

7. Report on the Zambia Roll Back Malaria baseline
study undertaken in 10 sentinel districts, July to August
2001. Zambia, RBM National Secretariat, 2001.
8. Akazili J. Costs to households of seeking malaria carein the Kassena-Nankana District of Northern Ghana. In:
Third MIM Pan-African Conference on Malaria, Arusha,Tanzania, 17–22 November 2002. Bethesda, MD,
Multilateral Initiative on Malaria: abstract 473.
9. Breman JG. The ears of the hippopotamus:
manifestations, determinants, and estimates of themalaria burden. American Journal of Tropical Medicineand Hygiene, 2001, 64(1,2 S):1–11.
10. Population and health in developing countries. Vol. 1.
Population, health and survival at INDEPTH sites.
Ottawa, International Development Research Centre,
2002.
11. Korenromp EL et al. Measuring trends in childhoodmalaria mortality in Africa: a new assessment of progress
toward targets based on verbal autopsy. [Lancet
Infectious Diseases, conditionally accepted, March 2003].
12. Trape J-F. The public health impact of chloroquine
resistance in Africa. American Journal of Tropical
Medicine and Hygiene, 2001, 64(1,2 S):12–17.
13. Grimwade K et al. HIV-infection in adults increases
rates of severe and fatal falciparum malaria in regions ofunstable transmission. In: XIVth International AIDS
conference 2002, Barcelona, Spain: abstract ThPeC7604.
14. Nwanyanwu OC et al. Malaria and humanimmunodeficiency virus infection among male employees
of a sugar estate in Malawi. Transactions of the Royal
Society of Tropical Medicine and Hygiene, 1997,91(5):567–569.
15. Mouchet J et al. Evolution of malaria in Africa forthe past 40 years: impact of climatic and human factors.
Journal of the American Mosquito Control Association,
1998, 14(2):121–130.
16. Sharp B et al. Malaria control by residual insecticide
spraying in Chingola and Chililabombwe, Copperbelt
Province, Zambia. Tropical Medicine and International
Health, 2002, 7(9):732–736.
17. The World Health Report 2001. Mental health: newunderstanding, new hope. Geneva, World HealthOrganization, 2001.

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