Reported incidence of dengue has increased worldwide
in recent decades, but little is known about its incidence in
Africa. During 1960–2010, a total of 22 countries in Africa
reported sporadic cases or outbreaks of dengue; 12 other
countries in Africa reported dengue only in travelers. The
presence of disease and high prevalence of antibody to
dengue virus in limited serologic surveys suggest endemic
dengue virus infection in all or many parts of Africa. Dengue
is likely underrecognized and underreported in Africa
because of low awareness by health care providers, other
prevalent febrile illnesses, and lack of diagnostic testing
and systematic surveillance. Other hypotheses to explain
low reported numbers of cases include cross-protection
from other endemic fl avivirus infections, genetic host
factors protecting against infection or disease, and low
vector competence and transmission effi ciency. Population-
based studies of febrile illness are needed to determine the
epidemiology and true incidence of dengue in Africa.
and Americas–Caribbean regions (1–3). In Africa, the
epidemiology and public health effect of dengue is not
clear. Aedes spp. mosquitoes are widely distributed in
Africa and can serve as vectors of dengue virus (DENV).
When their distribution is combined with rapid population
growth, unplanned urbanization, and increased international
travel, extensive transmission of DENV is likely in Africa
(Figure) (2,4). Over the past 5 decades, cases of epidemic
or sporadic dengue have been reported in many countries
in sub-Saharan Africa (5). Although sporadic cases of
dengue hemorrhagic fever (DHF) have been reported in a
few countries in Africa, no outbreaks have been reported
engue has emerged in recent decades as a worldwide
public health problem, particularly in the Asia–Pacifi c
(1). However, when compared with the Asia–Pacifi c and
Americas–Caribbean regions, the epidemiology and effect
of dengue in Africa has not been defi ned. A dengue outbreak
in Cape Verde was recently reported (>3,000 cases), and
the reappearance of dengue in Senegal after 20 years was
also reported (6). To estimate the extent of DENV infection
and dengue in Africa, we reviewed published literature and
other sources for reports of this disease in persons 1iving in
or traveling to this region.
Published, peer-reviewed literature, published and
unpublished country reports, and the World Health
Organization (WHO) library database, including Dengue
Net, were reviewed for 1960–2010 for the key terms
“dengue” and “Africa.” In addition, we examined peer-
reviewed published literature and other sources to
determine the extent of disease among travelers returning
from Africa. We searched for publications in English by
using MEDLINE and EMBASE electronic databases, Euro
Surveillance, and ProMED-mail posts. A review for dengue
reports in languages other than English did not fi nd any
reports that would change the conclusions of this article.
Additionally, references in each paper identifi ed during
searches were checked. Those references not already
identifi ed by the search were reviewed. Abstracts presented
at international forums were included if they contained
epidemiologic, entomologic, or virologic data pertaining to
dengue in Africa.
Reported Dengue in Africa
Dengue was reported in Africa in the late 19th and
early 20th centuries. Epidemics were reported in Zanzibar
(1823, 1870), Burkina Faso (1925), Egypt (1887, 1927),
South Africa (1926–1927), and Senegal (1927–1928)
(1,5,7). The epidemic in South Africa was confi rmed by
retrospective neutralizing antibody testing in the mid-
1950s, but the other reported epidemics were not laboratory
Dengue V irus Infec tion in Afric a
Ananda Amarasinghe, Joel N. Kuritsky, G. William Letson, and Harold S. Margolis
Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 17, No. 8, August 2011 1349
Author affi liations: International Vaccine Institute, Seoul, South
Korea (A. Amarasinghe, J.N. Kuritsky, G.W. Letson); and Centers
for Disease Control and Prevention, San Juan, Puerto Rico, USA
confi rmed and therefore may not have been dengue. During
the 50 years from 1960 through 2010, twenty laboratory-
confi rmed dengue outbreaks were reported in 15 countries
in Africa; most were from eastern Africa. Nearly 300,000
cases were reported in 5 large epidemics in the Seychelles
(1977–1979), Réunion Island (1977–1978), Djibouti
(1992–1993), Comoros (1992–1993), and Cape Verde
(2009) (6–9). DENV was fi rst isolated in Africa in Nigeria
in the 1960s (10). Subsequently, all 4 DENV serotypes have
been isolated in Africa (1). DENV-2 has been reported to
cause most epidemics, followed by DENV-1 (8,9).
Available data strongly suggest that DENV
transmission is endemic to 34 countries in all regions of
Africa (Figure; Table). Of these countries, 22 have reported
local disease transmission, 20 have reported laboratory-
confi rmed cases, and 2 (Egypt and Zanzibar) have reported
only clinical cases that were not laboratory confi rmed. In
the remaining 12 countries, dengue was diagnosed only for
travelers returning to countries to which dengue was not
endemic but never reported as occurring locally in these 12
Dengue among Travelers/Expatriates
Returning from Africa
The European Network on Imported Infectious Disease
Surveillance and other published data have reported 27
countries in Africa as locations where travelers/expatriates
from regions to which dengue was not endemic acquired
dengue (Table) (11–15). Among travel-acquired dengue
cases reported among persons from Europe, only 2%–8%
had visited Africa (11–14). Although 54%–61% and 25%–
31% of returning travelers with dengue returned from Asia
and Latin America, respectively, Africa seems somewhat
underrepresented with respect to dengue. However, this
fi nding is not the result of a paucity of visits among travelers
from countries to which dengue is not endemic.
Wilson et al. reported for the GeoSentinel Surveillance
Network of the International Society of Travel Medicine
and the Centers for Disease Control and Prevention that
travelers reporting illness have disproportionately visited
Africa (15). Febrile illness was more frequently reported for
travelers to sub-Saharan Africa (371 febrile illnesses/1,000
patients) than to any other region, followed by Southeast
Asia (248/1,000) and South America (143/1,000) (11).
Similar to reported global dengue endemicity patterns by
region, travelers with dengue came more frequently from
Southeast Asia and South America than Africa (11).
Prevalence of DENV Infection in Africa
Although outbreaks of dengue have been reported,
data on incidence or prevalence are not available for
Africa. A study in Nigeria determined the prevalence of
fl avivirus infections among 1,816 children and adults from
urban and rural areas in samples obtained mainly during
the early 1970s. Virus-specifi c hemagglutination inhibition
testing showed that the prevalence of immunity was 38%
for DENV-1 infection, 45% for DENV-2 infection, 43%
for yellow fever virus infection, and 49% for West Nile
virus infection (16). Serum specimens were also tested by
suckling mouse neutralization of DENV-2. The authors
concluded that because a high proportion of specimens with
antibody to DENV-2 were confi rmed by neutralization and
because many had only monotypic antibody, the prevalence
results were not likely confounded by cross-reactive
antibody to other fl aviviruses. In addition, this study showed
an increase in prevalence of antibodies against DENV with
age, which suggests endemic infection (16). Collenberg et
al. reported that the prevalence of antibodies against DENV
determined by immunoglobulin G indirect ELISA among
a sample of pregnant women and blood donors (n = 683)
was 26.3% in rural settings and 36.5% in urban settings in
Burkina Faso (17). However, in Cameroon, the prevalence
of antibodies against DENV determined by neutralization
testing among 256 adults was only 12.5% (18).
The prevalence of DENV infection found by these
studies was considerably lower than that found in dengue-
1350 Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 17, No. 8, August 2011
Figure. Dengue and Aedes aegypti mosquitoes in Africa. Brown
i ndicates 34 countries in which dengue has been reported,
including dengue reported only in travelers, and Ae. aegypti
mosquitoes. Light brown indicates 13 countries (Mauritania, The
Gambia, Guinea-Bissau, Guinea, Sierra Leone, Liberia, Niger,
Chad, Central African Republic, Republic of the Congo, Malawi,
Zimbabwe, and Botswana) in which dengue has not been reported
but that have Ae. aegypti mosquitoes. White indicates 5 countries
(Western Sahara, Morocco, Algeria, Tunisia, and Libya) for which
data for dengue and Ae. aegypti mosquitoes are not available.
Dengue Virus Infection in Africa
endemic areas of Asia and the Americas (19). However,
it is diffi cult to generalize from the small number of
studies in Africa because they had small sample sizes
and noncomparative age groups. Although the testing
method used for the studies in Nigeria and Cameroon
studies would minimize overestimation of DENV infection
prevalence because of cross-reactive antibodies to other
fl avivirus infections or yellow fever vaccination, use of an
immunoglobulin G ELISA in the Burkina Faso study did
not differentiate these infections.
Underrecognition of Dengue in Africa
In regions to which malaria is endemic, >70% of febrile
illnesses are treated as presumptive malaria, often without
proper medical examination and a laboratory diagnosis
(20,21). In a setting where diagnostic testing is conducted,
such as the GeoSentinel Surveillance Network, malaria
was found to be the predominant cause of systemic febrile
illness among travelers returning from sub-Saharan Africa
(622/1,000 patients) compared with dengue (7/1,000) (11).
This fi nding is not unexpected because malaria is more
endemic to Africa than other febrile illnesses. However,
overdiagnosis of malaria in areas of low transmission is
well documented, and overestimation by clinical diagnosis
is ≈61% (20,21). Many patients in Africa with fever are
designated as having fever of unknown origin or malaria
and remain without a diagnosis even if they fail to respond
to antimalarial drugs. Under these prevailing practices,
there is a real potential of misdiagnosing dengue as malaria.
In disease-endemic countries in the Asia–Pacifi c and
Americas–Caribbean regions, dengue accounts for 3%–
11% of febrile illnesses (19). Although dengue is well
recognized as a public health problem in these regions,
underreporting is common. Capture–recapture studies
in Puerto Rico showed that the degree of underreporting
and reporting in a passive surveillance system was ≈60%
(22). Wichmann et al. showed that in Thailand and
Cambodia underreporting of dengue was 1.4–9.6-fold
(23). A virologic study conducted in the Sudan among 100
consecutive hospitalized patients with fever reported that 21
cases were caused by DENV infection (24). Coupled with
the bias toward classifying most febrile illness as malaria,
we expect that there is substantial underrecognition and
underreporting of dengue in Africa.
During the 18th and 19th centuries, dengue was
recognized almost exclusively among colonial settlers and
military forces in Asia and the Americas and not among the
local population, probably as a consequence of inadequate
clinical investigation and surveillance (25). Similarly,
except for some reported local outbreaks, many cases of
dengue in Africa are more frequently reported among
travelers than among the local population, which suggests
lack of awareness, diagnostic facilities, and surveillance. In
Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 17, No. 8, August 2011 1351
Table. Countries in Africa with evidence of dengue virus
Type and country
Locally acquired, n = 7
Locally and travel acquired, n = 15
Angola 1986, 1999–2002‡
1779, 1887, 1927
1 and 2
1823, 1870, 2010‡
1 and 2
1 and 2
2 and 4
2 and 3
Travel/expatriate acquired, n = 12
*DRC, Democratic Republic of the Congo.
†Large local outbreaks.
‡TropNet Europ Network (www.tropnet.net) and ProMED mail
addition, travelers with febrile illness are frequently given
a misdiagnosis of malaria; a rate of misdiagnosis as high
as 77% has been reported (20). Of 27 countries in Africa
where travelers/expatriates acquired dengue, only 15 have
reported local disease transmission (Table). Therefore,
travel-acquired dengue appears to serve as a proxy for
identifying the underrecognition of dengue in Africa.
Factors Potentially Affecting Sustained
Transmission of DENV in Africa
Vector Effi ciency
Aedes aegypti mosquitoes, the principal DENV vector,
originated in Africa and spread to other countries in Africa
and other tropical countries in the 17th and 18th centuries
(1,3). Several other Aedes species mosquitoes, including
Ae. albopictus, Ae. africanus, and Ae. luteocephalus, are
found in Africa and are potential DENV vectors.
Urbanization is a major factor in facilitating the increase
of Aedes spp. mosquito populations (1). Accumulation of
nonbiodegradable, human-made containers in and around
living areas has provided the aquatic environment required
by these mosquitoes (25). Since the 1950s, a 3-fold increase
in urban human population density has occurred in Africa;
larger increases have occurred in Asia and the Americas (4).
With these demographic changes and subsequent increases
in Aedes spp. populations, increased DENV transmission
is likely to occur in Africa. For example, in Ghana, Aedes
spp. mosquito densities and biting rates seem suffi cient to
result in outbreaks of yellow fever and dengue (26).
Susceptibility of different
spp. mosquitoes to DENV has been shown to vary
geographically, and this variability may have implications
for DENV transmission and the epidemiology of the disease
in Africa. Mosquito strains in Africa have shown uniformly
low susceptibility to all 4 DENV serotypes in laboratory
settings (27–29). In addition, it has been well documented
that there are different susceptibilities of the vector to
different DENV genotypes; Ae. aegypti mosquitoes tend
to be more susceptible to infection with DENV-2 of the
Southeast Asian genotype than to the American genotype
(30). Similar fi ndings have been described for yellow
fever virus, and the reduced vector competence of strains
of Ae. aegypti mosquitoes from Asia has been suggested
as an explanation for the absence of this disease in Asia
(2,31). Reduced vector competence for DENV infection
in Africa may be an explanation for some of the apparent
low prevalence of DENV infection in Africa, although this
explanation must be confi rmed in appropriate studies.
Ae. albopictus mosquitoes are also potential
DENV vectors in Africa where they are considered
more anthropophilic than Ae. aegypti mosquitoes, more
susceptible to DENV infection, and are responsible for some
dengue outbreaks in Africa (29,32–33). However, similar to
studies with Ae. aegypti mosquitoes, experimental studies
with Ae. albopictus mosquitoes have demonstrated that
geographic variations in susceptibility to DENV infection
occur among different species (28,29). Furthermore, Ae.
albopictus mosquitoes are believed to be less effi cient as
an epidemic vector largely because of their differences in
host preferences and reduced vector competence, which
decreases the probability of sustained disease transmission
(34). Thus, appropriate ecologic studies are needed in
Africa to determine the relative roles of each species in
transmission of DENV.
Dengue is caused by 4 genetically related but
antigenically different viruses, and although it is uncertain
where DENV evolved, maintenance of all 4 serotypes in
enzootic cycles in Africa suggests that a progenitor virus
most likely originated in Africa (1). Despite the apparent
origin of DENV in Africa hundreds of years ago, the
more recent reported outbreaks appear to be the result of
virus introductions from Southeast Asia or the western
Pacifi c region and not the result of spillover from forest
transmission cycles. (25).
Vasilakis et al. reported that the rate of evolutionary
change and pattern of natural selection are similar among
endemic and sylvatic DENVs and suggested possible future
reemergence of DENV from the sylvatic cycle (35). Recent
experimental evidence suggests that emergence of endemic
DENV-2 from sylvatic progenitors may not have required
adaptation to replicate effi ciently in humans, implying that
sylvatic DENV-2 may reemerge (35). Existence of a silent
zoonotic transmission cycle affords a potential mechanism
for emergence of dengue in human populations and for
selection of virus variants with altered host range and
vector relationships (25).
Host genetic factors infl uencing pathogenesis
have been suggested to account for some variability in
susceptibility of DENV infection and disease expression
among different races. Halstead et al. provided evidence
of a dengue resistance gene in the black population (36).
During the 1981 and 1997 dengue epidemics in Cuba,
blacks were hospitalized with DHF/dengue shock syndrome
at lower rates than whites (37). This potential decreased
susceptibility to severe disease among the black population
and similar observations in Haiti have been used to support
the hypothesis that specifi c genomic difference among
different racial groups is a risk factor for DHF (36,38). This
hypothesis may provide an explanation for the observation
that, to our knowledge, outbreaks of DHF/dengue shock
syndrome have not been reported in Africa.
1352 Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 17, No. 8, August 2011
Dengue Virus Infection in Africa
Other prevailing diseases in Africa could provide
another hypothesis to explain the apparently low incidence
of dengue. Malaria, tuberculosis, and HIV infections are
endemic to many parts of Africa. Prevailing socioeconomic
and environmental factors may make populations in Africa
more vulnerable to these diseases than to dengue. Monath
(31) and Gubler (2) hypothesized that immunologic cross-
protection from heterotypic antibodies to other fl avivirus
infections (DENV and Japanese encephalitis virus) could
explain the absence of yellow fever virus in Asia. A similar
argument could be made to explain the low rate of DENV
infection caused by cross-protection from other endemic
fl aviviruses in Africa, but the extent to which it may exist
Dengue is a highly underrecognized and underreported
disease even in areas of the world where there is a high
level of public health and clinical awareness and diagnostic
capacity. In Africa, most febrile illness is not assessed
by laboratory diagnostics and is assumed to be malaria.
Sustained, systematic surveillance for dengue-like illness
combined with laboratory diagnostics and education of
health care providers has been the source of the information
about the public health role of dengue in Asia and the
Americas. This surveillance is needed in Africa to determine
the epidemiology and public health role of dengue.
The 2004 WHO Global Epidemiology of Infectious
Diseases Study estimated that 2.4% of global DHF cases
occurred in Africa and that 20% of the population in
Africa was at risk for dengue (39). However, because these
estimates were only for DHF and not dengue fever (DF),
a conservative approach to estimate DF in Africa would be
to apply the expected DHF to DF ratio of 1% to 5% to this
WHO study estimate. Thus, 0.2–1.0 million cases of DF
could be expected to occur in Africa on the basis of WHO
estimates of 10,000 cases of DHF in Africa, although no
DHF outbreaks have been reported.
Although there is some uncertainty about estimates
of cases provided by various sources, these estimates
provide a strong argument that DENV transmission is
present in Africa but likely underreported. Reported
outbreaks and dengue acquired by travelers to Africa from
regions to which dengue is not endemic indicate that local
transmission of DENV occurs in Africa. Furthermore, the
apparent increase of dengue in the region is the result of an
increase in the disease, consequence of improved disease
reporting, or both. Nevertheless, the epidemiology of
DENV transmission and the incidence of dengue in Africa
are poorly defi ned.
Dengue is usually not among the differential diagnoses
of acute febrile illness in Africa. Reasons for this lack of
inclusion are as follows: 1) malaria is the most prominent
endemic febrile illness in Africa and does not require
complex clinical and laboratory diagnostic facilities; 2)
a low awareness of dengue may contribute to health care
workers not considering the disease; 3) dengue is not a
reportable disease in most countries in Africa; 4) dengue
surveillance and diagnostics are not widely and consistently
available throughout Africa; and 5) funding for surveillance
and other research activities pertaining to dengue in Africa
are limited (8,9). For these reasons, improved surveillance
and laboratory diagnosis of fevers in Africa is a priority
and fi rst step in assessing the incidence of dengue in Africa.
Whether populations in Africa are susceptible to
DENV infection and disease at rates comparable with
those in populations in Asia or the Americas and the true
incidence of dengue in these countries cannot be determined
from data obtained from occasional reports of disease
outbreaks. Given that safe and effective dengue vaccines
should become available within the next decade (40),
questions regarding dengue incidence and epidemiology in
Africa must be answered by using appropriately designed
surveillance studies. Studies to determine the extent of
DENV infection among persons of all ages with febrile
illness could be included in other studies (e.g., malaria)
being conducted in the region and would provide answers
to speculation about dengue in Africa that has existed for
We thank Jeffrey Hanna for reviewing the manuscript and
providing valuable comments.
The Pediatric Dengue Vaccine Initiative Program was
supported by the Bill and Melinda Gates Foundation (grant no.
Dr Amarasinghe is a medical epidemiologist at the Pediatric
Dengue Vaccine Initiative Program, International Vaccine
Institute, Seoul, South Korea. His primary research interests
include dengue, hepatitis, and vaccine and immunization safety.
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Address for correspondence: Ananda Amarasinghe, Pediatric Dengue
Vaccine Initiative, International Vaccine Institute, Seoul National
University Research Park, San 4-8 Bongcheon-7 Dong, Kwanak-gu,
Seoul 151-919, South Korea; email: email@example.com
1354 Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 17, No. 8, August 2011