Rezza, Giovanni

Annali dell'Istituto Superiore di Sanità

E
D
IT
O
R
IA
L
Giovanni Rezza
Editorial
Ebola: when a nightmare becomes reality
Dipartimento di Malattie Infettive, Parassitarie ed Immunomediate, Istituto Superiore di Sanità, Rome, Italy
Ann Ist Super Sanità 2014 | Vol. 50, No. 4: 000-000
BACKGROUND INFORMATION
Ebola virus disease (EVD) was firstly identified in the 
Democratic Republic of Congo (DRC) and in Sudan 
in 1976, about nine years after the identification of the 
hemorrhagic fever due to the Marburg virus, another 
member of the Filoviridae family. Since most patients 
affected by Ebola do not develop frank hemorrhages, 
the formerly known term “Ebola hemorrhagic fever” has 
been replaced by “EVD”, to raise clinical suspicion and 
facilitate early recognition of the disease in absence of 
hemorrhagic symptoms.
The ebolavirus genus includes five different species: 
Zaire, Sudan, Taϊ Forest , Bundibugyo, and Reston [1].
During less than four decades, between 1976 and 
2012, 24 Ebola outbreaks have occurred in several 
Central African countries: DRC, Sudan, Gabon, the 
Republic of Congo (RC), and Uganda. Interestingly, 
the number of cases and outbreaks of EVD increased 
since the year 2000. Registered outbreaks, involving 
from a minimum of one up to a maximum of 425 in-
dividuals, were mainly caused by two different Ebola 
species: Zaire ebolavirus and Sudan ebolavirus. Such 
Ebola outbreaks are devastating in terms of high case-
fatality rates (ranging from 25% to 51% for Bundibu-
gyo ebolavirus, from 41% to 71% for Sudan ebolavirus, 
from 44% to 90% for Zaire ebolavirus), but they are 
usually controlled by applying public health measures 
consisting in early isolation of patients, contact tracing 
and quarantine of exposed people and/or entire villages 
(cordon sanitaire). A lower case-fatality rate was ob-
served in one outbreak which occurred in Uganda and 
was caused by the so-called Bundybugio strain. Another 
Ebola species, Reston ebolavirus, causing viral disease 
among simians and pigs in Asia, may infect also humans 
but without causing disease. Finally, before the current 
outbreak, only one case of Ebola due to a different virus 
species (Taϊ Forest ebolavirus), was reported in West-
ern Africa, in a researcher dissecting an affected ape in 
Ivory coast [2]. 
Traditionally, Ebola outbreaks origin from a single 
case (i.e., a man going into the forest to hunter wild 
animals), which is followed by nosocomial amplifica-
tion. Although fruit bats of the Pteropodidae family are 
assumed to represent the natural reservoir of the infec-
tion, other animal species living in the tropical rainfor-
est, such as non-human primates (gorillas and chim-
panzees) and antelopes, may acquire and introduce the 
infection into human populations through close contact 
with blood, secretions, organs or bodily fluids [3]. Then 
Ebola may spread through human-to-human transmis-
sion via direct contact with the body and/or bodily fluids 
of infected deceased persons, especially in the health 
care setting or in the household, or during traditional 
burial ceremonies. In such cases, the virus is supposed 
to enter human body through broken skin or mucous 
membranes. Infected persons develop EVD symptoms 
after an incubation period of about 4-11 days (range: 2 
to 21 days) [1, 2, 4].
THE 2014 OUTBREAK IN WEST AFRICA
On March 2014, when Ebola cases were identified 
in a remote area of Guinea, there was no much con-
cern about this news. At most, Ebola experts were a bit 
surprised by the geographical location of the outbreak 
epicenter. In fact, West Africa was not considered an 
area at high risk for EVD.
Although unexpected in terms of geographical lo-
calization, the Ebola outbreak in Guinea was initially 
considered just a further episode of the historical series 
of reappearance and disappearance of Ebola in Africa. 
Thus, for few months, it was almost ignored or, at least, 
underestimated.
The site of emergence of this outbreak was the re-
gion of Guéckédou, in the Guinea’s remote southeast-
ern forest area, near the border with Liberia and Sierra 
Leone. In a few months, Ebola crossed the borders rav-
aging the three countries, and reaching the capital cities 
of Conakry, Monrovia and Freetown. By October 29, 
2014, a cumulative number of more than 13 700 cases 
was reported by WHO. The case-fatality in the current 
West African outbreak appears to be around 50% when 
based on WHO official data, but it may be as high as 
70% in hospital case series [2, 4].
LESSONS TO BE LEARNT
Four major issues and caveats regarding the past and 
the future of this epidemic need to be discussed. In par-
ticular, we may take advantage from possible answers to 
questions raised by the emergence and the rapid spread 
of Ebola in West Africa: 
i) what is the extent of the areas at risk for Ebola
emergence in Africa? 
As mentioned before, with the exception of a single 
human case caused by the Taϊ Forest species of Ebola
Giovanni Rezza
E
D
IT
O
R
IA
L
virus, this is the first outbreak which occurred in West-
ern Africa. The agent involved in the current outbreak 
is Zaire ebolavirus, which was previously isolated in the 
DRC, RC, and Gabon. Phylogenetic analyses suggest 
that the Zaire ebolavirus strain found in Guinea is a 
distinct strain from that identified in Central Africa [5]. 
Further analyses of Ebola virus genomes from patients 
in Sierra Leone showed that the West African variant 
diverged from central Africa lineages around 2004. The 
genetic similarity across the strains sequenced dur-
ing the outbreak suggests a single cross-species pas-
sage from the natural reservoir followed by sustained 
human-to-human transmission [6]. Thus, these data 
suggest the presence of natural reservoirs for Zaire eb-
olavirus in West Africa; 
ii) why did the first Ebola outbreak in West Africa be-
come so large? 
There may be several answers to this question. First 
of all, Ebola was not expected to emerge in this area of 
the African continent, which is instead affected by the 
continued reemergence of another hemorrhagic fever: 
Lassa fever. Secondly, the original epicenter of the out-
break in Guinea was localized near the highly porous 
borders with the other two countries; the high human 
mobility across borders and from remote to urban ar-
eas might have influenced epidemic dynamics favoring 
the rapid spread of the infection [1, 7]. On the other 
hand, public health response was impaired by the need 
of intergovernmental coordination, along with logisti-
cal problems caused by poor infrastructures in areas 
devastated by civil wars [7]. Thus, delayed intervention 
due to logistical problems in the context of high popula-
tion mixing may explain the rapidly growing epidemic 
dimensions;
iii) can we quantify the risk of Ebola spreading beyond
the borders of currently affected countries? 
Since the beginning of the outbreak, few cases of 
Ebola have been reported in other African countries, in 
Europe, and in the US. 
In Nigeria, a cluster of 20 cases followed the introduc-
tion of the virus through a traveler who left Liberia after 
developing symptoms suggestive of EVD. However, the 
outbreak was rapidly contained. Single cases were also 
imported in Senegal (where there were no secondary cas-
es) and in Mali, through people traveling from Guinea. 
Another outbreak due to Zaire ebolavirus has been 
reported in Northern DRC this year, causing 66 cases 
of EVD before being contained; phylogenetic analyses 
have shown that it is not related to the West Africa out-
break.
In Spain, a nurse acquired Ebola after caring a mis-
sionary repatriated from Sierra Leone, whereas two cas-
es were identified in Dallas, Texas, in health care work-
ers who treated a traveler from Liberia who developed 
EVD symptoms after arriving in the US [8].
These findings suggest that Ebola may be contained 
when single cases are imported in other African coun-
tries. Although the introduction of single cases of EVD 
from affected countries to industrialized countries may 
occur, a large outbreak in a completely different context 
is unlikely. Moreover, exit screening of travelers from 
affected countries may reduce the risk of importation 
of Ebola cases [9];
iv) how can we deal with Ebola in terms of treat-
ment and prevention? 
Although there is no cure available at the moment, 
there are several experimental treatments that should 
be rapidly assessed, from antiviral drugs to monoclonal 
antibodies (i.e., the so-called ZMapp). Moreover, vac-
cine candidates which have proved to be effective in an-
imal trials are being tested in humans [10-12]. The need 
for effective drugs and vaccines claims for accelerated 
testing procedures and relaxed ethical considerations. 
Meanwhile, traditional public health measures should 
be strengthened in order to contain the outbreak in 
countries with sustained transmission of the infection. 
CONCLUSIONS
The Ebola outbreak in West Africa has been defined 
by WHO as a “public health emergency of international 
concern” and urges to be brought under control. To this 
end, international response is necessary to support af-
fected African countries, providing more hospital beds, 
individual protective equipment, and technical assis-
tance, in order to improve outbreak management and 
supportive care. 
In West Africa, a nightmare has become reality, and 
we cannot remain asleep: leaving Africa alone for too 
long would have unpredictable consequences, not only 
for poor-resource countries, but for the entire world.
1. Fedmann H, Geisbert TW. Ebola haemorrhagic fe-
ver. Lancet 2012;377:849-62. DOI: 10.1016/S0140-
6736(10)60667-8.
2. WHO. Ebola virus disease. Fact sheet N° 103. Update Sep-
tember 2014. Available from: www.who.int/mediacentre/
factsheets/fs103/en.
3. Leroy EM, Kumulungui B, Pourrut X, et al. Fruit bats as
reservoirs of Ebola virus. Nature 2005;438:575-6. DOI:
10.1038/438575a
4. WHO Ebola Response Team. Ebola virus disease in
West Africa – The first 9 months of the epidemic and for-
ward projections. N Engl J Med 2014;371:1481-95. DOI 
10.1056/NEJMoa1411100.
5. Baize S, Pannetier D, Oestereich L, et al. Emergence of
Zaire Ebola virus disease in Guinea – Preliminary report. 
N Engl J Med 2014; 371:1418-25. DOI: 10.1056/NEJ-
Moa1404505.
6. Gire SK, Goba A, Andersen KG, et al. Genomic sur-
veillance elucidates Ebola virus origin and transmission 
during the 2014 outbreak. Sciencexpress 2014. Available 
from: www.sciencemag.org/content/early/2014/08/27/sci-
ence.1259657.full.pdf?explicitversion=true
REFERENCES
Ebola: whEn a nightmarE bEcomEs rEality
E
D
IT
O
R
IA
L
7. Bausch DG, Schwarz L. Outbreak of Ebola virus disease
in Guinea: where ecology meets economy. PLOS Neglected 
Tropical Diseases 2014;8(7),e3056. Available from: www.
plosntds.org/article/info%3Adoi%2F10.1371%2Fjournal.
pntd.0003056.
8. WHO. Situation report-25 October 2014. Available from:
www.who.int/csr/disease/ebola/en/
9. Bogoch II, Creatore MI, Cetron MS, et al. Assessment
of the potential for international dissemination of Ebola
virus via commercial air travel during the 2014 west Af-
rican outbreaks. The Lancet, Early Online Publication, 21 
October 2014. DOI: 10.1016/S0140-6736(14)61828-6. 
10. Enserink M. Ebola drugs still stuck in lab. Science
2014;345:364-5. DOI: 10.1126/science.345.6195.364
11. Enserink M. Debate erupts on “repurposed” drugs for
Ebola. Science 2014;345:718-9. DOI:   10.1126/scien-
ce.345.6198.718
12. Feldmann H. Ebola-a growing threat? N Engl J Med
2014;371(15):1375-8. DOI: 10.1056/NEJMp1405314.
Epub 2014 May 7.


Ebola: when a nightmare becomes reality

http://www.annali-iss.eu/article/download/85/70

Ebola: when a nightmare becomes reality

Abstract

Similar works

Full text

Available Versions

Annali dell'Istituto Superiore di Sanità