On March 21, 2014, the Guinea Ministry of Health reported the outbreak of an illness
characterized by fever, severe diarrhea, vomiting, and a high case-fatality rate (59%)
among 49 persons (1). Specimens from 15 of 20 persons tested at Institut Pasteur in
Lyon, France, were positive for an Ebola virus by polymerase chain reaction (2). Viral
sequencing identified Ebola virus (species Zaïre ebolavirus), one of five viruses
in the genus Ebolavirus, as the cause (2). Cases of Ebola viral disease (EVD) were
initially reported in three southeastern districts (Gueckedou, Macenta, and Kissidougou)
of Guinea and in the capital city of Conakry. By March 30, cases had been reported
in Foya district in neighboring Liberia (1), and in May, the first cases identified
in Sierra Leone were reported. As of June 18, the outbreak was the largest EVD outbreak
ever documented, with a combined total of 528 cases (including laboratory-confirmed,
probable, and suspected cases) and 337 deaths (case-fatality rate = 64%) reported
in the three countries. The largest previous outbreak occurred in Uganda during 2000–2001,
when 425 cases were reported with 224 deaths (case-fatality rate = 53%) (3). The current
outbreak also represents the first outbreak of EVD in West Africa (a single case caused
by Taï Forest virus was reported in Côte d’Ivoire in 1994 [3]) and marks the first
time that Ebola virus transmission has been reported in a capital city.
Characteristics of EVD
EVD is characterized by the sudden onset of fever and malaise, accompanied by other
nonspecific signs and symptoms such as myalgia, headache, vomiting, and diarrhea.
Among EVD patients, 30%–50% experience hemorrhagic symptoms (4). In severe and fatal
forms, multiorgan dysfunction, including hepatic damage, renal failure, and central
nervous system involvement occur, leading to shock and death. The first two Ebolavirus
species were initially recognized in 1976 during simultaneous outbreaks in Sudan (Sudan
ebolavirus) and Zaïre (now Democratic Republic of the Congo) (Zaïre ebolavirus) (5).
Since 1976, there have been more than 20 EVD outbreaks across Central Africa, with
the majority caused by Ebola virus (species Zaïre ebolavirus), which historically
has demonstrated the highest case-fatality rate (up to 90%) (3).
The wildlife reservoir has not been definitively ascertained; however, evidence supports
fruit bats as one reservoir (6). The virus initially is spread to the human population
after contact with infected wildlife and is then spread person-to-person through direct
contact with body fluids such as, but not limited to, blood, urine, sweat, semen,
and breast milk. The incubation period is 2–21 days. Patients can transmit the virus
while febrile and through later stages of disease, as well as postmortem, when persons
contact the body during funeral preparations. Additionally, the virus has been isolated
in semen for as many as 61 days after illness onset.
Diagnosis is made most commonly through detection of Ebola virus RNA or Ebola virus
antibodies in blood (5). Testing in this outbreak is being performed by Institut Pasteur,
the European Mobile Laboratory, and CDC in Guinea; by the Kenema Government Hospital
Viral Hemorrhagic Fever Laboratory in Sierra Leone; and by the Liberia Institute of
Biomedical Research. Patient care is supportive; there is no approved treatment known
to be effective against Ebola virus. Clinical support consists of aggressive volume
and electrolyte management, oral and intravenous nutrition, and medications to control
fever and gastrointestinal distress, as well as to treat pain, anxiety, and agitation
(4,5). Diagnosis and treatment of concomitant infections and superinfections, including
malaria and typhoid, also are important aspects of patient care (4).
Keys to controlling EVD outbreaks include 1) active case identification and isolation
of patients from the community to prevent continued virus spread; 2) identifying contacts
of ill or deceased persons and tracking the contacts daily for the entire incubation
period of 21 days; 3) investigation of retrospective and current cases to document
all historic and ongoing chains of virus transmission; 4) identifying deaths in the
community and using safe burial practices; and 5) daily reporting of cases (4,7,8).
Education of health-care workers regarding safe infection-control practices, including
appropriate use of personal protective equipment, is essential to protect them and
their patients because health-care–associated transmission has played a part in transmission
during previous outbreaks (4,9).
Efforts to Control the Current Outbreak
To implement prevention and control measures in both Guinea and Liberia, ministries
of health with assistance from Médecins Sans Frontières, the World Health Organization,
and others, put in place Ebola treatment centers to provide better patient care and
interrupt virus transmission. Teams from CDC traveled to Guinea and Liberia at the
end of March as part of a response by the Global Outbreak Alert and Response Network
to assist the respective ministries of health in characterizing and controlling the
outbreak through collection of case reports, interviewing of patients and family members,
coordination of contact tracing, and consolidation of data into centralized databases.
Cases are categorized into one of three case definitions: suspected (alive or dead
person with fever and at least three additional symptoms, or fever and a history of
contact with a person with hemorrhagic fever or a dead or sick animal, or unexplained
bleeding); probable (meets the suspected case definition and has an epidemiologic
link to a confirmed or probable case); confirmed (suspected or probable case that
also has laboratory confirmation).*
In late April, it appeared that the outbreak was slowing when Liberia did not report
new cases for several weeks after April 9, and the number of new reported cases in
Guinea decreased to nine for the week of April 27 (Figure 1). Since then, however,
the EVD outbreak has resurged, with neighboring Sierra Leone reporting its first laboratory-confirmed
case on May 24, Liberia reporting a new case on May 29 that originated in Sierra Leone,
and Guinea reporting a new high of 38 cases for the week of May 25.
As of June 18, the total EVD case count reported for all three countries combined
was 528, including 364 laboratory-confirmed, 99 probable, and 65 suspected cases,
with 337 deaths (case-fatality rate = 64%). Guinea had reported 398 cases (254 laboratory-confirmed,
88 probable, and 56 suspected) with 264 deaths (case-fatality rate = 66%) across nine
districts (Figure 1). Sierra Leone had reported 97 cases (92 laboratory-confirmed,
three probable, and two suspected) with 49 deaths (case-fatality rate = 51%) across
five districts and the capital, Freetown. Liberia had reported 33 cases (18 confirmed,
eight probable, and seven suspected) with 24 deaths (case-fatality rate = 73%) across
four districts.
Major challenges faced by all partners in the efforts to control the outbreak include
its wide geographic spread (Figure 2), weak health-care infrastructures, and community
mistrust and resistance (10). Retrospective case investigation has indicated that
the first case of EVD might have occurred as early as December 2013 (Figure 1) (2).
To control the outbreak, additional strategies such as involving community leaders
in response efforts are needed to alleviate concerns of hesitant and fearful populations
so that health-care workers can care for patients in treatment centers and thorough
contact tracing can be performed. Enhancing communication across borders with respect
to disease surveillance will assist in the control and prevention of more cases in
this EVD outbreak.
In June 2014, the World Health Organization, via the Global Outbreak Alert and Response
Network, requested additional support from CDC and other partners, necessitating the
deployment of additional staff members to Guinea and Sierra Leone to further coordinate
efforts aimed at halting and preventing virus transmission. Persistence of the outbreak
necessitates high-level, regional and international coordination to bolster response
efforts among involved and neighboring nations and other response partners in order
to expeditiously end this outbreak.