EBOLA VIRUS SEMINAR!

EBOLA VIRUS DISEASE: TRANSMISSION, DIAGNOSIS, PREVENTION AND CONTROL

A

SEMINAR

PRESENTED

BY

OKOLI OBY

ON BEHALF OF EBOLA COMMITTEE MEMBERS

During

AMLSN NAUTH CHAPTER GENERAL MEETING

10TH SEPTEMBER, 2014

Introduction

•Infections with Ebola viruses cause a severe disease in humans, Ebola Virus disease (EVD). Since the first documented EVD outbreak in Zaire (now: the Democratic Republic of Congo) in 1976, five(5) species of the genus Ebola virus  (Filoviridae family) have been identified from samples collected from humans and non-humans primates during outbreaks of the diseases:

•Zaire ebolavirus (EBOV),

• Sudan ebola virus,

•Reston ebola virus,

•Tai Forest ebola virus and

•Bundibugyo ebola virus (Li  and Chen 2013, Edmond et al, 1977).

Ebola and Marburg, are among the most virulent pathogens of humans, causing severe hemogrrhagic fever that resembles fulminant septic shock (Bausch et al. 2003).

Signs and Symptoms

The average time between contracting the infection and the start of symptoms is 8-10days, but it can vary between 2 and 21 days (CDC, 2014)

•Flu-like stage

•Fatigue

•Fever

•Headache

•Joint pain

•Muscle and abdominal pain (Gatherer, 2014; CDC, 2014)

•Vomitting

•Diarrhoea

•Loss of appetite (CDC, 2014)

Less common symptoms include:

•Sore throat

•Chest pain

•Hiccups

•Shortness of breath

•Trouble swallowing (CDC, 2014)

•Maculopapular rash (in about 50% of cases) (Hoenen et al. 2006)

•Bleeding from puncture sites and mucous membrane (40-50% of cases)

•Vomitting of blood

•Coughing  it up

•Blood in the stool

Impaired blood clotting (Hoenen et al., 2006.

Classification

GROUP: Group V (-)ssRNA)

ORDER: Mononegavirales

FAMILY: Filoviridae

GENUS: Ebolavirus

SPECIES: 
.Ebola Virus
.Bundbugyo ebolavirus
.Reston ebolavirus
.Sudan ebolavirus
.Tai-Forest ebolavirus

Ebolavirus Virion Structure (Borio, et al., 2002)

Epidemiology

•The disease typically occurs in outbreaks in tropical regions of sub-saharan Africa (Ebola virus disease fact sheet, 2014).

•From 1976 (when it was first identified) through 2013, the World Health Organization reported 1,716 confirmed cases (Ebola virus disease Fact sheet, 2014).

•The largest outbreak to date is the ongoing 2014 West Africa Ebola virus outbreak, which is affecting Guinea, Sierra Leone, Liberia, Senegal and Nigeria (CDC, 2014).

•As at 13th August 2014, 2,127 cases have been identified, with 1,145 deaths (CDC, 2014)

Mode of Transmission and Contacting the EVD

•Diseases caused by EBOV in general are the most severe of
the viral hemorrhagic fevers. Humans are usually infected with
EBOV through close or direct contact with the contaminated
blood, secretions, tissues, organs and/or excretion of Viremic
animals, including patients with filovirus infections.

•Airborne transmission has not been documented. Person to
person transmission is considered the principal mode of
transmission for human outbreaks, regardless of how the
index case was infected.

•Transmission through sexual contact may occur up to seven
weeks after clinical recovery is observed for MARV, and it is
supposed to be possible for Ebola viruses. (Martini and
Schmidt, 1968).

•Transmission to humans can also occur by contact with dead
or living infected animals e.g. Primates (Monkeys and
Chimpanzees), forest Antelopes, Porcupines, and Bat
(European centre for Disease prevention and control, 2014)

•Bats remain the most likely, but still unconfirmed, reservoir
host for Ebola viruses (Wood et al, 2012, Pourrut et al, 2007).

•To date, the reservoir of the virus in West Africa is unknown.

•EBOV can survive in liquid or dried material for a number of
days (Piercy et al, 2010). Freezing or refrigeration will not
inactivate Ebola virus (European Center for Disease prevention
and Control, 2010, WHO, 2013, Chepurnov et al, 1995)

Figure 3. Modes of infection of the Ebola virus (Basler, et al., 2003)

Life cycle

•The ebolavirus life cycle begins with virion attachment to specific cell-surface receptors, followed by fusion of the virion envelope with cellular membranes and the concomitant release of the virus nucleocapsid into the cytosol. The viral RNA polymerase (L), encoded by the Ebolavirus RNA polymerase gene (L gene), partially uncoats the nucleocapsid and transcribes the genes into positive-strand mRNAs, which are then translated into structural and nonstructural proteins. Ebolavirus RNA polymerase binds to a single promoter located at the 3’ end of the genome. Transcription either terminates after a gene or continues to the next gene downstream. This means that genes close to the 3’end of the genome are transcribed in the greatest abundance, whereas those toward the 5’end are least likely to be transcribed. The gene order is therefore, a simple but effective form of transcriptional regulation. The most abundant protein produced is the nucleoprotein, whose concentration in the cell determines when L switches from gene transcription to genome replication. Replication results in full-length, positive-strand antigenomes that are, in turn, transcribed into negative-strand virus progeny copy. Newly synthesized structural proteins and genomes self-assemble and accumulate near the cellular membrane they bud from. The mature progeny particles then infect other cells to repeat the cycle. The Ebola Virus genetics are difficult to study due to its virulent nature (Feldmann Iet al., 2005)  

Figure 12. Generalized Inhibition of Immune Response (Crary, et al., 2003)

Ebola virus causes destabilization of the vascular endothelium leading to hemorrhage (Empig & Goldsmith, 2002)

Paradigm of Key Events in Ebolavirus Pathogenesis in Primates (Empig, & Goldsmith, 2002).

Pathophysiology

Endothelial cells, mononuclear phagocytes and hepatocytes are

the main targets of infection.

RISK OF TRANSMISSION ACCORDING TO

TYPE OF CONTACT WITH AN INFECTED

PATIENT:

•Very low or no recognized risk:- 
 Casual contact with a feverish, ambulant,
self – caring patient. E.g: sharing a sitting
area or public transportation, receptionist
tasks.

•Low risk:- Close face to face contact with a
feverish and ambulant patient. E.g: physical
examination, measuring temperature and
blood pressures.

•Moderate risk:- Close face to face contact
without appropriate personal protective
equipment (including eye protection) with a
patient who is coughing or vomiting, has
nose bleeds or who has diarrhea.

•High risk:- Percutaneous, needle stick or
mucosal exposure to virus – contaminated
blood, bodily fluids, tissues or laboratory
specimens in severely ill or known positive
patients.

LABORATORY DIAGNOSIS

•Real time quantitative RT-PCR

•Antigen-capture enzyme-linked immunosorbent assay (ELISA)

•Virus Isolation, (2). Reverse transcription –PCR (RT-PCR)

•Antigen detection by immunostaining

PREVENTION  AND CONTROL
•Behavioural Changes:

•Quarantine: Quarantine, also known as enforced
isolation is usually effective in decreasing spread.For
Ebola infections, notably with EBOV, the goal of
outbreak control is to interrupt direct human–to
human transmission through the early identification
and systematic isolation of cases, timely contact
tracing, proper personal protection, safely conducted
burials, and improved community awareness about
risk factors of Ebola infection and individual
protective measures (WHO, 2012, Dowell et al,
1995). Quarantine of infected patients has been
shown to effectively stop the spread of the disease in
previous outbreaks.
•The risk for infection can be significantly reduced
through the appropriate use of infection control
precautions such as wearing protective clothing,
including masks, gloves, gowns and goggles (CDC,
2014b) and adequate and strict barrier nursing
procedures (European Center for Disease Prevention
and Control, 2014, Francesconi et al, 2003).

•Vaccine: No vaccine is currently available for humans (Ebola virus Fact sheet, 2014)

PREVENTIVE APPROACHES FOR

HEALTHCARE WORKERS INCLUDE:

•Protective Measure:

      -- Pre test

–Test

–Post test

•Full compliance to vaccinations (notably
yellow fever) and malaria prophylaxis as
recommended for the target region.

•Sensitization for viral hemorrhagic fever
symptoms before working in endemic
countries strict implementation of barrier
management, use of personal protective
equipment, and disinfection procedures, as
per specific guidelines.

Suspicion of Exposure to Ebola Virus:

•A person suspected of having been
exposed to Ebola virus should be evaluated
and assigned a level of risk of transmission
using the criteria described earlier. If the
risk of transmission is considered low or
moderate, the person should be reassured
and asked to monitor his/her temperature
for 21 days. If the risk of transmission is
deemed high, active monitoring of health
status should be implemented immediately
and a medical evacuation should be
considered at an early stage.

MANAGEMENT
•No ebolavirus specific treatment exists
(Choi and Croyle, 2013).
•Treatment is primarily supportive in
nature and includes minimizing invasive
procedures, balancing fluids and
electrolytes to counter dehydration,
administration of anticoagulants early in
infection to prevent or control
disseminated intravascular coagulation,
administration of procoagulants late in
infection to control bleeding, maintaining
oxygen levels, pain management, and the
use of medications to treat bacterial or
fungal secondary infections (Bausch
et al., 2007).
•Early treatment may increase the
chances of survival. A number of
experimental treatments are being
studied.

CONCLUSION
•No approved therapy is available for the
treatment of these diseases, but progress
has been made in new experimental
approaches to post exposure prophylaxis
that are effective in Laboratory primate
(Bowen et al, 1978, Bwaka et al, 1999, Center for Disease control and
Prevention, 1989 (CDCP) CDCP, 1996,
CDCP, 2001, Conrad et al, 1978, Drosten
et al, 2002, Feldman et al, 2003).
•Supportive treatment is given to
patients. In Nigeria, seven patients
suffering from EVD have been treated
and discharged. 

THANK YOU
FOR YOUR
AUDIENCE!