Ebola Virus Disease

Abstract

The epidemic of Ebola haemorrhagic disease in West Africa is the most extensive to date, where the outbreak notably involved three West African countries with distant spread to other countries. There are five identified subspecies of Ebola virus. The first viral species reported to have infected humans was in 1976 in what is now the Democratic Republic of the Congo near the Ebola River. Ebola virus is an enveloped RNA virus about 80 x 800-1400 nm in size whose survival is dependent on an animal reservoir. An international team of researchers have sequenced 99 Ebola virus genomes and also observed a rapid increase in its genetic variation. There are several ways in which the virus can be transmitted to others. Symptoms of EVD may appear anytime from 2 to 21 days after exposure to the virus, although 8-10 days is most common. Making a diagnosis of EVD in individuals with early infection is very difficult. It is strongly recommended that diagnostic tests, which have undergone an independent and international evaluation, be considered for use. Samples collected from patients are an extreme biohazard risk; laboratory testing on non-inactivated samples should be conducted under maximum biological containment conditions. Despite the use of experimental drugs during the outbreak, which included monoclonal antibodies (ZMapp), the WHO, identified that the reason most patients in American and European hospitals survived was due to the use of intravenous fluids and other supportive therapy, along with adequate monitoring, control of blood chemistry and other parameters. Results of an interim analysis of trial show vaccine to be highly efficacious, but more conclusive evidence is needed on its capacity to protect populations through herd immunity. Finally, addressing the challenges of EVD is largely dependent on the creation of infection control awareness with the contribution of all members of the community.

Full text

IOSR Journal of Dental and Medical Sciences (IOSR-JDMS)
e-ISSN: 2279-0853, p-ISSN: 2279-0861.Volume 16, Issue 8 Ver. IX (Aug. 2017), PP 71-74
www.iosrjournals.org
DOI: 10.9790/0853-1608097174 www.iosrjournals.org 71 | Page
Ebola Virus Disease
*Dr. Y. J. Peter,
Department of Medical Microbiology and Parasitology, College of Health Sciences, University of Abuja,
FCT, Nigeria.
Correspondence to: *Dr. Y. J. Peter
Abstract: The epidemic of Ebola haemorrhagic disease in West Africa is the most extensive to date, where the
outbreak notably involved three West African countries with distant spread to other countries. There are five
identified subspecies of Ebola virus. The first viral species reported to have infected humans was in 1976 in
what is now the Democratic Republic of the Congo near the Ebola River. Ebola virus is an enveloped RNA virus
about 80 x 800-1400 nm in size whose survival is dependent on an animal reservoir. An international team of
researchers have sequenced 99 Ebola virus genomes and also observed a rapid increase in its genetic variation.
There are several ways in which the virus can be transmitted to others. Symptoms of EVD may appear anytime
from 2 to 21 days after exposure to the virus, although 8-10 days is most common. Making a diagnosis of EVD
in individuals with early infection is very difficult. It is strongly recommended that diagnostic tests, which have
undergone an independent and international evaluation, be considered for use. Samples collected from patients
are an extreme biohazard risk; laboratory testing on non-inactivated samples should be conducted under
maximum biological containment conditions. Despite the use of experimental drugs during the outbreak, which
included monoclonal antibodies (ZMapp), the WHO, identified that the reason most patients in American and
European hospitals survived was due to the use of intravenous fluids and other supportive therapy, along with
adequate monitoring, control of blood chemistry and other parameters. Results of an interim analysis of trial
show vaccine to be highly efficacious, but more conclusive evidence is needed on its capacity to protect
populations through herd immunity. Finally, addressing the challenges of EVD is largely dependent on the
creation of infection control awareness with the contribution of all members of the community.
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Date of Submission: 09 -08-2017 Date of acceptance: 23-08-2017
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I. Introduction
Ebola virus disease (EVD) is a severe; potentially life threatening illness caused by Ebola virus.1, 2 Ebola virus is
one of the causes of the dreaded Viral Haemorrhagic Fevers (VHF). Viral Haemorrhagic Fevers are caused by
viruses of five distinct virus families: Arenaviridae, Bunyaviridae, Filoviridae, Flaviviridae and
Paramyxoviridae. Each of these families shares a number of features:
1. They are all Ribonucleic Acid (RNA) viruses and are all covered, or enveloped, in a fatty (lipid) coating.
2. Their survival is dependent on an animal or insect host, called the natural reservoir.
3. The viruses are geographically restricted to the areas where their host species live.
4. Humans are not the natural reservoir for any of these viruses. Humans are infected when they come into
contact with infected hosts. However, with some viruses, after the accidental transmission from the host,
humans can transmit the virus to one another.
5. Human cases or outbreaks of hemorrhagic fevers caused by these viruses occur sporadically and irregularly.
The occurrence of outbreaks cannot be easily predicted.
6. With a few noteworthy exceptions, there is no cure or established drug treatment for VHFs.
Data and relevant information were extracted from relevant publications and bulletins about the Ebola epidemic
in West Africa and other outbreaks of EVD.
Ebola Virus
Ebola virus disease is often a fatal disease that normally occurs in primates (such as monkeys, gorillas
and Chimpanzees) and recently in humans. Ebola virus disease is caused by an infection with a virus of the
family Filoviridae, genus Ebola virus.1, 2 The first viral species reported to have infected humans was in 1976 in
what is now the Democratic Republic of the Congo near the Ebola River.3 Ever since then, outbreaks have been
reported sporadically. There are five identified subspecies of Ebola virus. Four of the five have caused disease
in humans: Ebola virus (Zaire Ebola virus); Sudan virus (Sudan Ebola virus); Tai Forest virus (Taï Forest Ebola
virus, formerly Côte d’Ivoire Ebola virus); and Bundibugyo virus (Bundibugyo Ebola virus).1,2,3 The fifth,
Reston virus (Reston Ebola virus), has caused disease in nonhuman primates, but not in humans.3,4 However,

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DOI: 10.9790/0853-1608097174 www.iosrjournals.org 72 | Page
the natural reservoir host of Ebola virus still remains unclear. Although, on the basis of available evidence,
scientists believe that the virus is zoonotic (animal-borne) with fruit bats being the most likely reservoir.4,5 Four
of the five subtypes occur in animal host native to Africa while the Reston virus subtype was isolated from
specimens collected from the Philippines, however, this subtype is not known to cause human illness.
Ebola virus is an enveloped RNA virus about 80 x 800-1400 nm in size whose survival is dependent on an
animal reservoir.6 An international team of researchers have sequenced 99 Ebola virus genomes and also
observed a rapid increase in its genetic variation.7 In total, 99 EBOV genome sequences were generated from 78
confirmed EVD patients, representing more than 70% of the EVD patients diagnosed in Sierra Leone from late
May to mid-June; using multiple extraction methods or time points for 13 patients.8 Genetic similarity across the
sequenced 2014 samples suggests a single transmission from the natural reservoir, followed by human-to-human
transmission during the outbreak.8 However, more recent molecular data obtained from the outbreaks in Kikwit
and Gabon did not find any molecular evidence for adaptation during human to human transmission.9 Infection
results in severe disease with high mortality rate among infected humans and other primates.10 It has no known
cure or vaccine; treatment is only supportive.11 Ebola virus is considered a potential biological weapon
candidate.6
Ebola Virus Disease
Transmission occurs mainly in acutely ill patients.1,2 There are several ways in which the virus can be
transmitted to others, these include:
1. Direct contact with blood or body secretions such as sweat, saliva, semen or vaginal fluids of an infected
person
2. Exposure to objects (such as needles and other sharps) that have been contaminated with infected
secretions.
3. Exposure through friends and family members who are often the first care givers of cases.
4. Through health care personnel who are at risk of contracting the disease from cases in healthcare facilities.
Human to human transmission is usually a sequel to this by direct contact with the bodily fluids of symptomatic
infected persons, these accounts for the high rate of infection of health workers and subsequently nosocomial
infection.12
Clinical Presentation
Symptoms of EVD may appear anytime from 2 to 21 days after exposure to Ebola virus, although 8-10 days is
most common.
Typical symptoms include:
1. Headache, fever and chills
2. Malaise and weakness
3. Joint and muscle aches
4. Diarrhea and loss of appetite
5. Abdominal pain and vomiting
Diagnosis
Making a clinical diagnosis of EVD in individuals with early infection is difficult.3 However, having a high
index of suspicion would aid during outpatient triaging. If an individual presents the early symptoms of EVD
and there is suspicion of visit to or exposure to EVD exposed case, EVD should be considered, the patient must
be isolated and other health professionals notified. Confirmation that symptoms are caused by Ebola virus
infection are made using the following diagnostic methods:3
1. antibody-capture enzyme-linked immunosorbent assay (ELISA)
2. antigen-capture detection tests
3. serum neutralization test
4. reverse transcriptase polymerase chain reaction (RT-PCR) assay
5. electron microscopy
6. virus isolation by cell culture.
Careful consideration should be given to the selection of diagnostic tests, which take into account technical
specifications, disease incidence and prevalence, and social and medical implications of test results. It is
strongly recommended that diagnostic tests, which have undergone an independent and international evaluation,
be considered for use. Current WHO recommended tests include:3
1. Automated or semi-automated nucleic acid tests (NAT) for routine diagnostic management.

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DOI: 10.9790/0853-1608097174 www.iosrjournals.org 73 | Page
2. Rapid antigen detection tests for use in remote settings where NATs are not readily available. These tests
are recommended for screening purposes as part of surveillance activities; however reactive tests should be
confirmed with NATs.
The preferred specimens for diagnosis include:3
1. Whole blood collected in ethylenediaminetetraacetic acid (EDTA) container bottle from live patients
exhibiting symptoms.
2. Oral fluid specimen stored in universal transport medium collected from deceased patients or when blood
collection is not possible.
Samples collected from patients are an extreme biohazard risk; laboratory testing on non-inactivated
samples should be conducted under maximum biological containment conditions. All biological specimens
should be packaged using the triple packaging system when transported nationally and internationally.
Treatment
Standard treatment for EVD is still limited to supportive efforts, although medications and vaccines are still
undergoing clinical trials. Therapy consists of:
1. balancing the patient’s fluids and electrolytes,
2. maintaining their oxygen status and blood pressure, and
3. treating them for any other complicating infections
Note that oral or topical salt and water therapy does not give any benefit to the patient. Despite the use
of experimental drugs during the outbreak, which included monoclonal antibodies (ZMapp), the WHO,
identified that the reason most patients in American and European hospitals survived was due to the use of
intravenous fluids and other supportive therapy, along with adequate monitoring, control of blood chemistry and
other parameters.12 There is however hope for EVD management as researchers announced on 31st July, 2015
that a vaccine trial in Guinea had been completed that appeared to give protection from the virus. The vaccine is
a recombinant replication-competent vesicular stomatitis virus-based vaccine, expressing a surface GP of Zaire
Ebola virus (rVSV-ZEBOV).12 The vaccine, rVSV-ZEBOV, was studied in a trial involving 11 841 people
during 2015. Among the 5837 people who received the vaccine, no Ebola cases were recorded 10 days or more
after vaccination.3 Results of an interim analysis of the trial show the vaccine to be highly efficacious, but more
conclusive evidence is needed on its capacity to protect populations through herd immunity.12
Prevention
Prevention remains the major strategy in combating the spread of EVD. A number of measures aimed at
containing the spread of EVD at the individual, health facility and community levels include:
a) Individual level:
1. Individuals should observe a high index of suspicion for people (including friends and family members)
who are sick and suffer very high fever and anyone of the above mentioned symptoms.
2. Recent contacts with someone who had EVD or visited a community where there is outbreak of EVD calls
for caution.
3. Increased personal hygiene practice such as regular hand washing, bathing and use of personal protective
equipment.
b) Health Facility level:
1. Infection control measures/standard precautions should be taken in cases suspected to be EVD.
2. Enforce the use of personal protective equipment i.e, hand gloves, face mask and eye goggles by all
healthcare personnel at risk of exposure to blood and body fluids.
3. Suspected cases should be isolated and barrier nursed.
4. Appropriate disposal of all biological waste especially blood, body fluids, sharps and needles.
c) Community Level:
1. Increased community hygiene and environmental sanitation
2. Community members should notify health care workers (facilities) and appropriate authorities of any
suspected case(s).
3. Community should be educated properly about EVD and mobilized to observe safer cultural practices e.g.
circumcision, tattoo and traditional surgical practices.
4. Immediate burial of dead bodies should be practiced and the practice of touching dead bodies with bare
hands be avoided.
Finally, addressing the challenges of EVD is largely dependent on the creation of infection control awareness
with the contribution of all members of the community. All healthcare personnel, non-governmental

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DOI: 10.9790/0853-1608097174 www.iosrjournals.org 74 | Page
organization staff and medical students should lead information dissemination in the community and in private
discussions wherever they find themselves. Health care facilities personnel must insist that protective measures
are instituted in all healthcare facilities and hospitals.
References
[1]. CDC. Case Definition for Ebola for Ebola Virus Disease (EVD). http://www.cdc.gov/mmwr/volumes/65/su/su6503a6.htm.
Accessed 12/07/17
[2]. CMDA@ http://www.cmdanigeria.net/blog/ebola-virus-disease-facts-for-health/. Accessed 12/07/2017
[3]. WHO. Ebola virus disease. http://www.who.int/mediacentre/factsheets/fs103/en/. Accessed 12/07/2017
[4]. CDC. Ebola Haemorrhagic Fevers: signs and symptoms. http://www.cdc.gov/vhf/ebola/hcp/index.html. Accessed 12/07/16
[5]. Hoenen T, Groseth A, Falzaro D, Feldman. Trends in Molecular Medicine. Ebola Virus; unravelling pathogenesis to combat a
deadly disease. 12(5):206-215.
[6]. Adegboro B and Adeola A. O. Marburg Haemorrhagic fever; Recent advances, Afr. J. Cln. Exper. Microbiol. 5/2011; 12(2): 76-81
[7]. WHO. Ebola virus genome sequencing data published. Special programme for Research and Training in Tropical Diseases.
http://www.who.int/tdr/news/2014/ebola-virus-genome/en/. Accessed 18/12/16
[8]. Stephen K. G, Augustine G, Kristian G. A, Rachel S. G, Daniel J. P and others. Genomic surveillance elucidates Ebola virus origin
and transmission during the 2014 outbreak. Science. 12/09/2014; 345 (6202): 1369-1372.
[9]. Feldman H, Czub M, Jones S and Others. Emerging and re-emerging infectious diseases. Med. Microbiol. Immunol. 9/2002; 191:
63-74
[10]. Sanchez A, Geisbert T W and Feldmann H. Filoviridae; Marburg and Ebola viruses in: Knipe DM, Howley PM, Griffin DE, Lamb
RA, Martin MA, Roizman B, et al. editors, Fields virology, 5th edition Philadelphia: Lippincott Williams and Wilkins; 20096.
P.1409-48
[11]. Staples J. E, Belman RF and Powers A. M. Chikungunya Fever; An Epidemiological Review of a Re-emerging Infectious Disease.
8/2009; CID49:942-8.
[12]. Omilabu SA, Salu OB, Oke BO, James AB. The West African ebola virus disease epidemic 2014–2015: A commissioned review.
Niger Postgrad Med J. 2016; 23: 49-56.
*Dr. Y. J Peter. “Ebola Virus Disease.” IOSR Journal of Dental and Medical Sciences (IOSR-JDMS) , vol.
16, no. 08, 2017, pp. 01–12.