Epidemiology and control of the 2014 ebola virus disease outbreak in western africa: A narrative review of literature

The disease rendered wide spread devastation in the Sub Region causing the death of several thousands of infected cases before it was subsequently brought under control, draining significant resources. This study reviewed existing literature using the PRISMA statement for reporting systematic review as a guide. It sorts to describe the epidemiological and socio-economic factors that affected the Ebola Virus Disease (EVD) outbreak and to highlight the control measures implemented during the period.

Corresponding author: Ninsawu Nicholas Nakpan,

IPMPH, Hanoi Medical University

Email: nakpan4@yahoo.com

Received: 12/7/2018

Accepted: 18/11/2018

EPIDEMIOLOGY AND CONTROL OF THE 2014 EBOLA VIRUS

DISEASE OUTBREAK IN WESTERN AFRICA:

A NARRATIVE REVIEW OF LITERATURE

1 Ninsawu Nicholas Nakpan, 2 Stanley Gordon Fenwick

3 Le Minh Giang, 4 Pham Quang Thai, 5 Prosper Mandela Amaltinga

1 Institute of Preventive Medicine and Public Health, Hanoi Medical University, Vietnam

2

Fenwick Tufts University, United States; 3 Department of Global Health-Hanoi Medical University, Vietnam;

4

National Institute of Hygiene and Epidemiology, Vietnam;

5

Clinical Nursing Department, Nyaho Clinic-Ghana The 2014 West Africa Ebola outbreak was the largest outbreak of the disease on the continent and the globe at large, beginning December 2013 in Guinea The disease rendered wide spread devastation in the Sub Region causing the death of several thousands of infected cases before it was subsequently brought under control, draining significant resources This study reviewed existing literature using the PRISMA state-ment for reporting systematic review as a guide It sorts to describe the epidemiological and socio-economic factors that affected the Ebola Virus Disease (EVD) outbreak and to highlight the control measures implemented during the period Human interaction with the vegetation created exposure to the EVD and males had an overall incidence slightly higher than females whilst being a child was a significant risk of dying from the infection A weak health system and inadequate infrastructure in affected countries contributed largely to early spread International organizations’ collaborating with local partners formed an immense component to control-ling the outbreak Effective collaboration is required at international and national levels of the world to remain prepared for future outbreaks It calls for a ‘One Health’ approach to tackling future events

Keywords: Epidemiology, socio-economic factors, control, containment, implementation, West Africa

I INTRODUCTION

The world has been confronted in recent

years with a host of infectious diseases that

are either emerging or reemerging They have

included the zika virus infection, Mers-Cov,

SARS, Avian influenza and lastly, Ebola Virus

Disease (EVD) which gave the world a scare

during its outbreak in West Africa The former

Director General of the World Health

Organi-zation (WHO) described the 2014 Ebola virus

“unquestionably the most severe acute public

health emergency in modern times” [1] The

outbreak started in December 2013 in Guinea, followed by its spread in subsequent months

to neighboring Liberia and Sierra Leone The infection was later reported in Senegal, Mali, Nigeria and outside the African Region to Europe (Spain, Italy and England) and the USA [2; 3]

Ebola virus disease (EVD) is a rare and fatal disease [4] of zoonotic origin believed to have originated in a reservoir of fruit bats of

the family Pteropodidae So far there is no

specific treatment for this deadly infection First observed in humans in 1976, EVD has caused around 25 outbreaks to date [5; 6]; however, a yet to be licensed vaccine (rVSV-ZEBOV) is being administered to prevent transmission as is in the case of the ongoing outbreak in Democratic Republic of Congo

(DRC) declared on May 8, 2018 [7] Epidemics

have also occurred in Sudan, Gabon and

Uganda A non-human type of the virus known

as Ebola Reston Virus has also been found

present in the Philippines, affecting other

primates rather than humans [8] The Ebola

virus is transmitted to humans through contact

with infected living or dead animals, and its

propagation in the human population occurs

through human-to-human transmission of the

virus The most recent outbreak to have

caused significant devastation occurred in

West Africa with deaths totaling 11,300 as of

early September 2015 [6; 9; 10] EVD is

asso-ciated with a case fatality rate of 30% to 90%,

depending on the virus species [8] The index

case of the West Africa EVD outbreak was

identified to have originated in an under 2 year

old boy in Meliandou, Guinea [4; 5]

Prompt international response provided by

the World Health Organization, Médecins

Sans Frontières (MSF) and the Center for

Dis-ease Control during the early part of 2014

seemed to have helped in controlling the

out-break It, however, circulated rapidly across

borders due to ineffective tracking [11] The

recent outbreak in DRC starting in Bikoro has

recorded a total of 55 cases as of June 28,

2018 It includes 38 confirmed cases, 15

prob-able cases and 2 suspected cases, while 29

have died [12]

During the West Africa Ebola outbreak,

about $2.2 billion was lost in GDP in the three

worst affected countries, according to the

World Bank The disease resulted in lower

investment and a substantial loss in private

sector growth, with declining agricultural

pro-duction among other negative consequences

[13] An effective preparedness plan has been

the hallmark of rapid containment and controls

as was in the case of Senegal and DRC in

2017 [14]

This article aims to describe the

changes that affected the 2014 Ebola virus outbreak and highlight the control measures implemented during the West Africa Ebola outbreak from a review of existing literature

II METHODS

This study conducted a narrative review using the PRISMA statement for reporting sys-tematic reviews as a guide [15] To develop this study, 52 published articles were re-viewed, published from 2013 to 2017 Articles selected for retrieval were assessed for meth-odological validity prior to inclusion in the re-view using standardized critical appraisal in-struments from the Joanna Briggs Institute (JBI) Assessment and Review Instrument for

an observational, qualitative and quantitative study

The review focused on full-text articles published in English and French with an option

to translate into English It also examined the reports of conferences and meetings of or-ganizations and stakeholders The articles extracted were biased to those that have been published during the past 5 years to enable it

to capture the most recent development in the field When the titles of the retrieved articles were insufficient to determine eligibility, the abstracts were read to determine if they could

be included A thorough search was extended

to the websites of major international agencies such as the World Health Organization, the

US Centers for Disease Control (CDC), the Pan African Medical Journal (PAMJ) and bibli-ographies of indexed papers Search terms

socio-economic factors, and containment and

con-trol efforts A specific search for appropriate

articles began with a few of the keywords

above to include a large collection of articles

It then narrowed the search using the following

syno-nyms: Epidemiological factors AND

socio-economic factors AND control measures OR

containment AND Implemented AND Ebola

Virus Outbreak OR Ebola hemorrhagic fever

AND West Africa Information obtained from

the search databases and other sources were

saved using the Zotero software

775 articles were identified from the

data-base search which related to the topic in

addi-tion to 97 articles from bibliographies, agency

websites and grey literature (Figure 1) The

inclusion criteria included articles with

informa-tion on Ebola epidemiology or its control in

West Africa The exclusion criteria included all

articles with information other than the Ebola

outbreak in West Africa, its epidemiology and

control measures implemented during 2014

Out of a total of 872 articles identified, 490 articles were duplicated and 382 non-duplicate articles were screened further for inclusion

216 articles were further excluded after title and abstract screening was done These did not meet the inclusion criteria because they covered information of the Ebola virus out-break that occurred in other places outside of West Africa Sixty articles were excluded after full text screening because the information did not relate specifically to the epidemiology and control of the EVD outbreak in 2014 Thirty-two (32) were excluded because they focused only on describing the clinical features of the disease; 14 articles focused only on Socio-economic aspect of the Ebola outbreaks that occurred in other parts of Africa rather West Africa; 8 articles were non-specific in describ-ing control programs implemented durdescrib-ing the outbreak in 2014 in West Africa Fifty-two (52) studies were finally included in this review due

to it having relevant information on the epide-miology and control of EVD outbreak in 2014

The prisma flow chart

Figure 1 PRISMA Flow diagram for systematic review [15]

III RESULTS

1 Epidemiological factors affecting the

2014 West African EVD outbreak

Several epidemiological investigations

have been conducted in affected countries to

provide a better understanding of the disease

and to institute mechanisms to contain or

con-trol the disease The basis of such

investiga-tions has often been demonstrated to be

nec-essary in making available information for

clinical and preventive decisions

1.1 The vegetation

There are a number of studies that have

argued the role of ecological forces in sparking

outbreaks of Ebola [9 - 10] The environment

provides a special space for interaction

be-tween human population and animals

Gue´cke´dou in Guinea’s remote

southeast-ern forest region is thought to be the epicenter

of the Ebola virus infection that spans into

various regions of Guinea as well as to

neighboring Liberia and Sierra Leone [10]

Ebola virus required two transmission

proc-esses for outbreaks to emerge It required an

initial spillover event referring to a zoonotic

transmission from either the primary Sylvan

reservoir or from a secondary host for whom

the virus is pathogenic It is then accompanied

by a second process which is a

person-to-person spread from the index case occurring

from the spillover infection [8] Human

popula-tion density and their interacpopula-tion with sylvan

habitat creating pressure in the landscape

may have opened a channel for EVD spillover

into human communities The human

popula-tion’s interaction with the vegetation paved the

way for a zoonotic otic transmission [8]

Hunt-ing and consumHunt-ing fruit bats is suspected as the likely way humans were exposed to the infection in Guinea [16] In a study in 2014, [10], the authors agreed that biological and ecological factors may drive emergence of the virus from the forest, but suggested that socio-political landscape dictated where the virus went next

1.2 The distribution of Ebola virus dis-ease

In Conakry, Guinea and surrounding pre-fectures, a descriptive study analyzed data involving 1355 cases reported During the study period, the overall number of EVD cases per 100,000 persons was 33.2 in Conakry, 89.3 in Coyah, 37.5 in Dubreka, 136.9 in Fore-cariah, and 24.6 in Kindia [17] (See Table 2) Cumulative incidence was slightly higher among males (46.8 cases/100.000 persons) than females (45.3 cases/100.000 persons) Furthermore, incidence varied by sex in pre-fectures; incidence was higher among female residents in Coyah, Forecariah and Kindia (Table 2)

A descriptive retrospective study in Sierra Leone, amongst other findings confirmed a high infectivity among males than was ob-served in the opposite sex group [13]

A descriptive study using 4.955 probable and confirmed cases in the same country how-ever, showed a slightly contrasting finding [14; 18] It showed that the ratio of male to female EVD cases, irrespective of the district of origin, was 1:1 This means there was an equal inci-dence between males and females It however maintained that EVD affected all age groups with the most affected age groups being be-tween 26-45 years old (Table 3)

Table 2 Ebola virus disease cases by prefecture and sex in Conakry and surrounding

prefectures in Guinea, January 1, 2014 – March 29, 2015 [17]

Table 3 Aggregated age-specific case fatality in Western Area Region, Sierra Leone,

June 2014 – November 2015 [14]

1.3 Risk of mortality from EVD

Most EVD patients were likely to die of the

infection as opposed to surviving due to the

high case fatality [18] Being a child was a risk

factor of dying from an Ebola infection [19] In

Sierra Leone, this study found that younger

age of life and diarrhea at presentation was

significantly associated with death The case fatality rate was highest in infants, at approxi-mately 70% [19] Progression to death accord-ing the authors was swift and the overall death rate was high Diarrhea at presentation would worsen the infection and doubled the risk for death in children [19]

Age group (years) Totals cases (N) %missing records Dead (N)

Age-specific fatality (%)

A similar age-specific fatality rate was

iden-tified in WA in Sierra Leone from June 2014-

November 2015 [14] The age-specific fatality

rate was highest for children below the first

year of age (73%) In the Moyamba district in

Sierra Leone, a different picture was noted in

relation to the risk of dying from EVD Here,

among the 88 patients admitted to the

Moyamba Ebola Treatment Center, 31

pa-tients tested positive for Ebola virus The age

range of patients was from 3 months to 85

years An overall case fatality of 58% was

reported and the study found no significant

correlation between age and fatal outcome

[20] It related fatal outcomes to the clinical

features of patients who died 83% compared

to 46% in survivals

1.4 Risk of exposure and transmission

of EVD

Contact with bodily fluids and secretions as

well as organs of infected animals, either

hunted or found dead, can lead to introduction

of EVD into the human population [19; 21] It

usually starts from a single animal

transmis-sion to humans Amplification then takes place

via human-to-human spread [2; 18]

Person-to-person transmission of Ebola

virus involves close personal contact with

in-fected person through skin ulcers or mucous

membrane and has been a source of

trans-mission in the West Africa outbreak [4; 8]

Body fluids contacted from infected persons

such as semen, oral secretions, urine, feces

and handling human corpses during burial

activities poses a risk This review found that

healthcare workers particularly are thought to

be at higher risk when they work in unhygienic

and unprotected conditions [21; 22] A key

finding of a study dissociated the belief of a

link between healthcare workers dedicated to EVD settings and contracting the disease [13] Burial ceremonies serve as a vehicle of spread when mourners or relatives come into direct contact with the body of the deceased

A study in the three most affected countries in Africa found out that 25% of cases of EVD who reported any exposure in the outbreak reported exposures at funerals About 65% of these cases reported having touched the corpse It was greatest in Guinea (71%) and least for Liberia (61%) [23] Non-funeral con-tacts such as direct physical contact and bod-ily fluids contributed in driving the EVD trans-mission [24] In Nigeria, frequent exposure among health workers was through physical contact, accounting for 73% of infections among health care workers [25]

2 Socio- economic factors affecting the

2014 Ebola outbreak

2.1 Family interaction and social prac-tices

Notable drivers of the Ebola outbreak transmission were the role family played, practices such as marriage and funerals and other social events such as migrations and markets Rural people are heavily dependent

on and trust their immediate family in times of crisis [26; 27] Marriage and funerals met a need to understand Ebola risks from the per-spective of family and its notions of unavoid-able social obligations During an outbreak like EVD, such social activities become a driver for transmission [3; 27] A funeral of the wife of a chief in a chiefdom in Guinea border is be-lieved to have generated an Ebola outbreak in Daru which spread to the neighboring Sierra Leone town Fogbo [27]

2.2 Inadequate and weakened health

system and lack of trust in services

Several included studies identified an

in-adequate, weakened health system and the

lack of trust in these where they existed as the

fulcrum of the EVD spread during the outbreak

[28 - 33] The three most affected countries

(Guinea, Sierra Leone, Liberia), had been

re-ported to have less functional or weak health

systems contributing to delayed effective

diag-nosis, laboratory confirmation of cases and an

overall unpreparedness [34; 35] Risk of dying

was higher in intense transmission countries

with scarce or overstretched health facilities

[31] In places where basic facilities existed,

the facilities were often closed because they

lacked well-trained personnel, particularly in

Guinea, or essential medication among others

[32; 33] The absence of effective surveillance

systems and other public health infrastructure

impeded the ability of affected countries to

effectively detect and respond to the rapid and

lethal outbreak [4]

There was little trust in the government and

most health care facilities during the early

pe-riod of the West Africa outbreak of Ebola

Communities did not trust interventions

com-ing from central government and the most

pre-ferred treatment were traditional cures For

example, in the Ugandan outbreak, people

feared that once they went to hospital they

would never see their families again [36]

Stigma arising from isolation and quarantine in

health institution further fueled the fears and

trust of suspected cases [37]

2.3 Bush meat consumption

Bush meat is both an economic benefit and

a source of protein to most people in West

Africa The consumption and use of bush meat

is found to be a primary source of the spill-over of EBV wildlife reservoirs to humans [33; 35] Bush meat in Liberia is a critical source of protein, estimated to account for three-quarters of the country’s meat use [36] A sur-vey of 277 households in 73 locations in Libe-ria indicated that consumption of bush meat in households had decreased Perceived risk of bush meat consumption had a significant in-fluence on this outcome [38]

3 Control measures implemented dur-ing the EVD outbreak in West Africa

Early response is a vital component to con-trolling an outbreak such as Ebola Virus dis-ease The containment of the West Africa Ebola outbreak placed a significant strain on both international and national resource ca-pacity

3.1 Logistic provision and management

Logistic availability both as response experts and material logistics were very vital to the control of the 2014 Ebola outbreak in West Africa Essentially, logistics came in as finances, erection of Ebola treatment units, and the provision of isolation wards, personal protective equipment (PPE), laboratory equip-ment and medical supplies [11]

The World Health Organization collabo-rated with the United Nations in 2014 to coor-dinate a system-wide response across agen-cies It used the STEPP strategic framework which sought to stop the outbreak, treat the infected, ensure essential services, preserve stability and prevent further outbreaks [22] The International Medical Corps (IMC) in cooperation with local health ministries oper-ated 5 ETUs in Sierra Leone and Liberia be-tween September 15, 2014, and December

31, 2015 It assumed management of the

ETUs and provided a laboratory, clinic and an

effective data collection [39] The IMC

col-lected clinical and epidemiological data in the

most difficult circumstance where infection

control was regarded paramount

Provision of beds to Ebola Holding Centers

(EHCs) and Community Care Centers (CCCs)

averted an estimated 56.000 cases in Sierra

Leone between June 2014 and February 2015

[40] Emergency Management Centers (EMC)

with increased bed capacity and

improve-ments in detection and treatment were opened

in the Kailahun district in Sierra Leone This

resulted in an increase in the proportion of

patients admitted to EMC from 35% to 83%

[41]

3.2 State-related interventions

In late July 2014, the Liberia ministry of

Health and social welfare (MOHSW)

imple-mented an Incident Management System

(IMS) with support from the CDC, WHO and

other partners Upon cooperation with

interna-tional partners, they provided technical

activi-ties such as case management, contact

trac-ing, safe burials, surveillance, and laboratory

and social mobilization [42] The Liberian

gov-ernment enforced a quarantine for

asympto-matic individuals suspected to have come in

contact with EVD positive cases and

crema-tion of bodies of deceased cases [43] The

paper observed responses managed by

state-related actors created an atmosphere of fear

and mistrust

In July 2015, the Men’s Health Screening

Programme (MHSP) was implemented in

Libe-ria by the Ministry of Health in collaboration

with other partners The screening provided

vital assistance to control measures by identi-fying Ebola survivors who tested positive to Ebola in their semen and improving behavior change in the community [44]

3.3.Travel restrictions

The constant and massive movement of people and goods across the world makes national boundaries meaningless, at least in terms of disease transmission Many countries resorted to border closures, heightening entry and exit airport screening, restricting flights to affected countries and banning passengers from affected countries, seen as quite a con-troversial decision [42; 45]

IV DISCUSSION

The search for articles on EVD outbreak generated several results due to the large amount of literature published after the out-break in West Africa, however, few articles related to the specific objectives of this study with the entry of specific keyword terms Spillover events could have occurred from the resultant interaction between human popu-lation density and vegetation in affected re-gions [5; 10] The increasing activities of hu-mans in response to settlement or develop-mental needs have created a platform for the exposure of humans to zoonotic diseases These activities have altered population densi-ties around vegetation which could be serving

as home to the reservoir of the Ebola virus It

is worthy to note that not all cases of animal spillovers led to outbreaks in humans [46] Conflicts, need of land for human settlement and economic activities including harvesting of wood for charcoal burning and hunting has over the years created a complex web of

rela-tionships which could have contributed to the

spread of the Ebola virus [8; 10] Humans can

be infected from close contact with the

secre-tions, organs, blood or other bodily fluids of

infected animals These animals have been

either hunted or found ill or dead in the

rainfor-est [21; 23] Amplification of the virus has

come from human-human spread of the virus

through close contact with the body fluid or

secretions of an infected person Body fluids

of infected people or those that have died of

EVD pose significant danger to close contacts

or health workers who may be handling these

people without appropriate protection

The overall incidence of EVD in the West

Africa outbreak was slightly higher in males

than females This difference, though biased

towards males, was not significant Different

study sites showed different outcomes, even

in the same country Overall cumulative

inci-dence in the capital city of Guinea was slightly

higher in men though in three surrounding

prefectures, incidence of EVD was higher in

females (Table 2)

Table 3 shows EVD infectivity to be higher

in males in the healthcare workers WAR with

all age groups This is likely because males in

healthcare settings may be tasked with the

transport of patients, handling corpses of the

dead since women are less culturally involved

in this regard It can therefore be concluded

that the incidence of Ebola among sex groups

depended on exposure factors such as

do-mestic, social and economic responsibilities of

the individuals Women’s domestic role in

tak-ing care of the sick usually places them at risk

of contracting EVD [10; 17] Women in Africa

usually are involved in trade and sometimes

travel distances for this, heightening their risk

of exposure to EVD during the outbreak

Mortality from EVD was highest in children [14; 19] and even more severe before the first year of life [8; 19] Children progressed swiftly towards death with a median time of three days For example in Moyamba district of Si-erra Leone, in an Ebola Treatment Center, 31 patients tested positive for Ebola virus Diar-rhea was significantly more common in those who died (83%) as compared to those that survived Diarrhea raised the risk of death from EVD The study did not find any correla-tion between age and fatal outcome [8] Chil-dren are more vulnerable because they easily become dehydrated from diarrhea and this could account for the increased mortality in such instances

The 2014 West Africa Ebola Virus outbreak laid bare an age long problem of the continent and most importantly the sub-region This per-haps was a bitter exposure of the sub-region’s inadequacies as a significant number of pre-cious lives were lost It was estimated as of August 31, 2014, about 3.685 cases were con-firmed and suspected cases were recorded-which rose through 2016 to over 28.000 [48; 49] Severely affected countries were already bedeviled by burden of extreme poverty, re-cent history of civil conflict, and weak health-care systems Sierra Leone, Liberia, and Guinea are among the countries with the world’s lowest levels of public investment in health, the fault lines along which the EVD outbreak exploded [26 - 28]

Unavailable laboratory facilities to enhance diagnosis of EVD at the early onset of the out-break was a significant hindrance to early re-sponse [30] Lack of approved diagnostic tools adapted to such a large-scale outbreak, staff shortage and limited biosafety knowledge and weak national laboratory systems[50] were

driving factors of transmission Improving the

overall laboratory systems will capacitate

countries’ preparedness against future

out-breaks

Healthcare workers may have incurred

considerable risk in either the hospital or their

community, especially given the difficulty in

making a clinical diagnosis of EVD at the

on-set [33] It was easy to misdiagnose EVD in

the early onset of the outbreak since it was

clinically similar to febrile conditions common

to these countries such as malaria and

ty-phoid Healthcare workers therefore may have

had significant exposure in the formal or

infor-mal practice of their profession

Implementa-tion of a triage system in Kenama, for

in-stance, led to a significant decline in the

num-ber of EVD cases in healthcare workers [51]

Much was reported of affected

communi-ties refusing healthcare assistance due to lack

of trust in the healthcare system [36; 50; 51]

The African society is built strongly around

close family ties In the African context, most

people, especially those in rural areas, relied

heavily on immediate and extended family for

support in times of material needs or health

challenges This may have accounted for the

observation of some included studies that

found trust to be highest among households

[52] This could explain why the outbreak

spread easily during its onset It is however

difficult to delineate this trust in family from

possible factors such as the economic status,

availability and distance to healthcare

institu-tions as likely factors influencing family trust

Available evidence from articles reviewed

in this study also underscored the influence of

social obligations and cultural practices on the

potential driving of EVD [3; 52] The

perform-ance of these social functions such as mar-riage and funeral ceremonies provided an ave-nue for interaction between family and com-munity members Marriage and responsibilities

of individual spouses and families were a con-tributing factor to the spread of the Ebola out-break as this study identified As a matter of domestic responsibility, women took care of ill spouses and in some cases relatives to pro-vide feeding, cleaning of clothes and environ-ment where such patients lived Handling of corpses and burial activities was a significant source of exposure and spread of the Ebola virus disease in West Africa

This study also purposed to review the measures that were implemented to control the EVD outbreak in 2014 Much international support has included the shipment of large quantities of personal protective equipment, diagnostic laboratory apparatus and vehicles Medical and logistic advisors from MSF, the

US Center for Disease Control & Prevention, and WHO aided in the disease control [53] Early response came in the form of expertise and provision of essential material or financial logistics Aside the CDCs early response role acknowledged in the introduction of this review, other organizations deployed huge number of its response work force to the

overwhelmed by the outbreak [43]

All articles included in this study for the purpose of reviewing the control measures echoed the significant impact of the interna-tional organizations had on containing and controlling the spread of the Ebola outbreak Some important ones captured by this study referred to the role the WHO played in coordi-nation with several intercoordi-national or local agen-cies [38]