Journal of Family Medicine and Primary Care

REVIEW ARTICLE
Year
: 2019  |  Volume : 8  |  Issue : 7  |  Page : 2189--2201

Ebola virus: A global public health menace: A narrative review


Shamimul Hasan1, Syed Ansar Ahmad2, Rahnuma Masood3, Shazina Saeed4,  
1 Department of Oral Medicine and Radiology, Faculty of Dentistry, Jamia Millia Islamia, New Delhi, India
2 Department of Oral Surgery, Faculty of Dentistry, Jamia Millia Islamia, New Delhi, India
3 Department of Conservative Dentistry, Faculty of Dentistry, Jamia Millia Islamia, New Delhi, India
4 Department of Amity Institute of Public Health, Amity University, Noida, Uttar Pradesh, India

Correspondence Address:
Dr. Shazina Saeed
Department of Amity Institute of Public Health, Amity University, Noida, Uttar Pradesh - 201 303
India

Abstract

Ebola virus disease (EVD), a fatal viral hemorrhagic illness, is due to infection with the Ebola virus of the Filoviridae family. The disease has evolved as a global public health menace due to a large immigrant population. Initially, the patients present with nonspecific influenza-like symptoms and eventually terminate into shock and multiorgan failure. There exists no specific treatment protocol for EVD and only supportive and symptomatic therapy is the line of treatment. This review article provides a detailed overview of the Ebola virus; it's clinical and oral manifestations, diagnostic aids, differential diagnosis, preventive aspects, and management protocol.



How to cite this article:
Hasan S, Ahmad SA, Masood R, Saeed S. Ebola virus: A global public health menace: A narrative review.J Family Med Prim Care 2019;8:2189-2201


How to cite this URL:
Hasan S, Ahmad SA, Masood R, Saeed S. Ebola virus: A global public health menace: A narrative review. J Family Med Prim Care [serial online] 2019 [cited 2019 Dec 7 ];8:2189-2201
Available from: http://www.jfmpc.com/text.asp?2019/8/7/2189/263755


Full Text



 Introduction



Ebola, earlier termed as Ebola hemorrhagic fever (EHF), is a critically lethal ailment which primarily affects the humans and nonhuman primates. Ebola virus disease (EVD) occurs due to a virus infection which belongs to the family Filoviridae and genus Ebolavirus.[1] EVDs has posed diagnostic challenges and has been a universal public health threat since its discovery. While investigating an alleged yellow fever case, Dr. Peter Piot in the year 1976 first detected the disease in Zaire, Africa (presently the Democratic Republic of Congo).[2] The name “Ebola” was termed as the disease was noticed near the Ebola river in Congo.[3]

Fruit bats of Pteropodidae family, such as Hypsignathus monstrous, Epomops franqueti, and Myonycteris torquata serve as the natural hosts of the EBOV in Africa. Nonhuman primates may develop the infection by eating the partly eaten fruits and may also transmit the infection to humans.[4] Indian population is an impending threat to EVD, as India falls in the home range of Pteropodidae family of fruit bats.[5]

Ebola virus transmission primarily takes place through close bodily contact with the infected patient or their fluids, contaminated tissue surfaces, and clothing from alive, infected or deceased individuals. Unsafe traditional burial practices also play a pivotal role in the disease transmission.[6] There is documented evidence regarding the sexual mode of disease transmission, although transmission through the air is unlikely.[7]

EVD present with bizarre and atypical manifestations mimicking other viral diseases, especially in the initial disease phase. Constitutional symptoms, such as fever, myalgia, headache, vomiting, and diarrhea are the early presenting features. Hemorrhagic rash, internal and external bleeding are usually the warning manifestations in the late stages.[8] Bleeding from the body apertures is a distinguishing EVD manifestation.[9] Gum bleeding, odynophagia, and atypical oral manifestations constitute the oral features of EVD.[10]

Till date, there is no precise antiviral management or vaccination for EVD. The management protocol mainly relies on supportive and symptomatic therapy, along with monitoring coagulopathies and multiorgan dysfunction.[2]

The World Health Organization (WHO) affirmed the EVD outbreak as a “Public Health Emergency of International Concern” on August 8th, 2014.[5]

With the enormous immigrant population, India is estimating the likelihood of a probable EVD outbreak. The Ministry of Health and Family Welfare, Government of India, in collaboration with other agencies has appraised the situation and recommended travel instructions by air, land, and sea and health care professionals.[11]

 Taxonomy



The virus belongs to the Ebola virus genus, Filoviridae family, and Mononegavirales order.[12] The genus Ebolavirus includes the following species- Zaire ebolavirus (EBOV), Reston ebolavirus (RESTV), Bundibugyo ebolavirus (BDBV), Taï Forest ebolavirus (TAFV), Sudan ebolavirus (SUDV), and the newly identified Bombali ebolavirus (BOMV).[13] Except for exclusive identification of RESTV in the Philippines, all the other species causes endemic West African EVD.[14]

EBOV responsible for the EHF causes the highest human mortality (57%–90%), followed by SUDV (41%–65%) and Bundibugyo virus (40%). TAFV has caused only two nonlethal human infections to date, whereas RESTV causes asymptomatic human infections.[15]

[Figure 1] shows the taxonomy of Ebola virus.{Figure 1}

 Transmission



Based on the Centers for Disease Control and Prevention (CDC) classification, Ebola virus is considered as a biosafety level 4 and category A bioterrorism pathogen with an immense likelihood for massive nationwide transmission.[16]

 Source of Infection



Intimate physical contact with the patients in the acute disease stages and contact with the blood/fluids from the dead individuals constitutes the most important modes of transmission.[17]

The long-established funeral ceremonies in the African countries entail direct handling of the dead bodies, thus significantly contributing to the disease dissemination. Unsafe conventional burial procedures accounted for 68% infected cases in 2014 EVD outburst of Guinea.[18]

EBOV RNA may be identified for up to a month in rectal, conjunctival, and vaginal discharges and semen specimens may demonstrate the virus presence up to 3 months, thus signifying the presence of EBOV in recuperating patients.[14] The sexually transmitted case of EVD has been reported between a convalescent patient and close family member. Another study demonstrated a case in a recuperating male patient. The patient's semen specimen tested positive with Ebola viral antigen almost 3 months after the disease onset.[19]

Asymptomatic EBOV carriers are not infectious and do not have a major role play in the EVD outburst, and the field practice in Western Africa supported this assumption.[20] However, this presumption was refuted after the documentation of a pioneer asymptomatic carrier case in North Gabon epidemic (1996).[21]

EBOV has been detected from blood, saliva, semen, and breast milk, while RNA has been isolated from sweat, tears, stool, and on the skin, vaginal, and rectal swabs, thus highlighting that exposure to infected blood and bodily secretions constitute the major means of dissemination.[22]

Eating uncooked infected animal meat such as bats or chimpanzees account significantly to oral EVD transmission, especially in the African countries.[23] The demonstration of the Ebola virus in the Filipino pigs in 2008 triggered the likelihood of an extensive range of possible animal hosts.[24]

EVD dissemination has also been reported with hospital-acquired infections, particularly in areas with poor hygiene conditions. The infected needles usage was responsible for the 1976 EVD outbreak in Sudan and Zaire.[25],[26] Improper hygiene and sterilization were the crucial factors for the 1967 Yambuku EVD outburst.[27]

EVD dissemination may also occur through the inanimate materials with infected body secretions (fomites).[19] However, disease transmission through the airborne and droplet infection is ambiguous.[10]

[Figure 2] shows the primary and secondary transmission of disease.{Figure 2}

[Table 1] depicts the possible routes of transmission.{Table 1}

 Epidemiology



The vast majority of EVD cases and outbursts have been endemic to African continent ever since the disease detection in 1976,[28] and 36 such outbreaks have occurred in six African countries.[29]

[Table 2] shows Ebola epidemiological outbreaks between 1976 and 2014.{Table 2}

The 2014–2016 EVD started in South East Guinea rural surroundings and eventually became a global public health menace by rapidly disseminating to urban localities and other countries.[28]

[Figure 3] depicts the geographical distribution of Ebola virus disease.{Figure 3}

The conducive environmental surroundings of the African continent facilitate EVD endemicity. However, intermittent imported Ebola cases have also been noticed in United States, United Kingdom, Canada, Spain, and Thailand.[30],[31]

[Figure 4] depicts the distribution of Ebola virus disease in West African Countries.{Figure 4}

Out of the unparalleled globally reported 28,616 cases and 11,310 casualties, Liberia accounted for almost 11,000 cases and over 4,800 deaths.[32]

[Table 3] shows the statistics of the 2014–16 West African outbreak.{Table 3}

 Pathogenesis



Ebola viruses penetrate the human body through mucous membranes, skin lacerations/tear, close contact with infected patients/corpse, or by direct parental dissemination.[33] EBOV has a predilection to infect various cells of immune system (dendritic cells, monocytes, and macrophages), endothelial and epithelial cells, hepatocytes, and fibroblasts where it actively replicates by gene modulation and apoptosis and demonstrate significantly high viremia.[34] The virus reaches the regional lymph nodes causing lymphadenopathy and hematogenous spread to the liver and spleen promote an active inflammatory response.[35] Release of chemical mediators of inflammation (cytokines and chemokines) causes a dysregulated immune response by disrupting the vasculature system harmony, eventually causing disseminated intravascular coagulation and multiple organ dysfunction.[36]

[Figure 5] demonstrates the pathogenesis of Ebola virus disease.{Figure 5}

 Clinical Features



Due to the bizarre and atypical manifestations in the initial phase, mimicking dengue fever, typhoid fever, malaria, meningococcemia, and other bacterial infections, EVD poses diagnostic dilemmas.[37]

The incubation period ranges from 2 to 21 days. However, symptoms usually develop 8–11 days following infection.[38],[39]

The initial disease phase is represented by constitutional symptoms.[40] High-grade fever of >38o C is the most frequently reported symptom (85–95%), followed by other vague symptoms such as general malaise (85–95%), headaches (52–74%), dysphagia, sore throat (56–58%), and dry cough.[41],[42] The progressively advanced disease is accompanied by abdominal pain (62–68%), myalgia (50–79%), nausea, vomiting, and diarrhea (84–86%).[41]

Variety of hemorrhagic manifestations forms an integral component of the late disease phase.[38] Gastrointestinal tract bleeding manifests as petechiae, hematuria, melena, conjunctival bleeding, contusion, or intraperitoneal bleeding. Mucous membrane and venipuncture site bleeding, along with excess clot formation may also occur. As the features advances with time, the patients experience dehydration, confusion, stupor, hypotension, and multiorgan dysfunction, resulting in fulminant shock and ultimately death.[43],[44]

Maculopapular exanthema constitutes a characteristic manifestation of all Filovirus infection, including EVD.[45] The rash usually appears during the 5th to 7th day of disease and occur in 25–52% of patients in the past EVD outbreaks.[46]

[Table 4] shows the clinical manifestations of Ebola virus disease.{Table 4}

Although EVD has a number of similar features with other viral hemorrhagic fevers (e.g. dengue), there are differences that set them apart.

[Table 5] depicts the differentiating features of the Ebola virus and dengue virus infection.{Table 5}

Orofacial features

Gum bleeding, atypical mucosal lesions, and odynophagia comprise the distinctive oral manifestations. Epistaxis (nasal bleed), bleeding from venipuncture sites, conjunctivitis, and cutaneous exanthema are the other manifestations.[9] Bleeding tendencies and gum bleeding is not seen in asymptomatic or initial EBOV patients reporting to the dental hospital.

EVD dissemination in the field of oral and dental health may appear nonsignificant; although, probable situations which may pose a risk to dental health professional have been appraised by Samaranayake et al.[21] and Galvin et al.[10]

[Table 6] depicts the various orofacial manifestations of Ebola virus disease{Table 6}

 Diagnosis



EVD patients usually demonstrate altered laboratory parameters based on the stage of the disease.

[Table 7] shows the laboratory findings in Ebola virus disease.{Table 7}

The WHO (2014) recommended the sample collection of whole blood or oral swab at suitable centres called Ebola treatment centers.[47] Reverse transcriptase polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA) are the most frequently utilized tests for laboratory affirmation of the EVD.[43] RT-PCR is capable of detecting viral RNA in the blood samples of infected patients immediately after the commencement of signs and symptoms,[42],[48] has a high sensitivity (up to 100%), and gives results within 1–2 days in cases of epidemics. ELISA detects the immunoglobulins G and M in samples of infected patients, has a low sensitivity (91%) and is not suitable for initial affirmation during an outbreak.[42],[49]

 Prevention



The most imperative strategy in EVD is to avert the vulnerable population from getting infected and limit the transmission. These preventive strategies entail intensive and rigorous endeavors from the Government, public health amenities, medical units, and personals.[50]

The most essential aspect to curb EVD transmission is to avert direct bodily contact with infected individuals and their body fluids.[51]

Health caregivers are extremely vulnerable and experience an augmented professional threat for EVD.[52] Thus, scrupulous adherence to the universal infection control measures is fundamental in all the hospitals, laboratories, and other health care services.[53] The U.S. CDC has advocated the appropriate use of various personal protective equipment as a mandate for health care professionals.[50]

The risk of rapid importation of Ebola virus into human beings can be prevented by averting the direct bush meat and bats contact.[54]

Unsafe traditional burial procedures, especially in the African continent significantly contributed to the EVD transmission. Hence, it is essential to practice safe and guarded funeral rituals to prevent the disease spread.[55]

WHO recommends the implementation of safe sex practices to combat the sexual transmission of EVD. Strict abstinence or proper and regular condom use in male EVD survivors at least for a period of 12 months of the symptom onset or until their semen has twice tested negative should be followed.[56]

Dental health care personals are extremely susceptible to EVD as they are in regular contact with blood and saliva during the routine diagnostic procedures. There is no documented case of EVD through saliva till date. A study on the identification of EBOV in oral fluids affirmed that patients presenting with demonstrable serum levels of EBOV RNA also exhibit identifiable salivary levels.[57] The incubation period for all body fluids including saliva is 21 days; hence, oral health personals are vulnerable to develop the disease if universal infection control protocol is not followed.[58]

[Table 8] demonstrates the various infection control measures to prevent the Ebola virus spread.{Table 8}

[Box 1] shows the travel guidelines to EBOV affected regions.[INLINE:1]

 Treatment



Till date, there is no precise antiviral management or vaccination for EVD.[51] The management protocol mainly relies on supportive and symptomatic therapy. Public health strategies emphasizing on epidemiological surveillance, contact tracing, and quarantine of the patient have been recommended to combat the dissemination of EVD.[59]

Rehydration, adequate nourishment, analgesics, and blood transfusion form a keystone supportive treatment of EVD patient.[60] Intravenous fluids and oral rehydration solution endow with proper electrolytes substitute and maintain the intravascular volume. Unrelenting vomiting and diarrhea are taken care of by the use of antiemetics and antidiarrheal drugs.[35],[60],[61] Suspected cases of secondary bacterial infections and septicemia are best managed by the use of prophylactic antibiotic regimen (third generation I.V. cephalosporins).[62] Concurrent parasitic coinfections may also be seen and require prompt investigations and management.[63]

A number of investigative clinical trials emphasizing on the development of vaccine, antibody therapies, and antiviral drugs have been conducted for EVD.[64]

[Table 9] shows experimental treatment for Ebola virus disease.{Table 9}

Various clinical trials in Africa, Europe, and the United States suggest that Ebola vaccines are in various development stages (Phase I–III). A number of candidate vaccines employ diverse platforms, including recombinant viral vectors (most evolved vaccine candidate), DNA vaccines, inactivated viral particles, subunit proteins, recombinant proteins, and virus-like particles. Example of viral vectors expressing ebolavirus glycoproteins include recombinant simian adenovirus (cAd3), recombinant vaccinia virus, recombinant human adenovirus (Ad26), and a live vesicular stomatitis virus used alone or in prime-booster regimens.[65]

However, Ebola virus having the glycosylated surface proteins and preferentially infecting the immune cells impedes the development of an effective vaccine.[66]

 Dental Management



Dental health care professionals in Europe have not encountered a case of EVD so far. However, health care personals (including dental surgeons) are more prone to EVD while treating patients in West or sub-Saharan Africa. Dental professionals are more likely to encounter asymptomatic EVD patients or those with early-stage vague symptoms.[27]

Individuals with a travel history to Ebola endemic regions, but with no direct intimate contact with the disease fall in the low-risk category and may undergo any medical/dental health care procedures without restrictions. However, all the nonessential procedures should be postponed for 21 days in individuals with direct exposure to the virus. The regional Health Service Executive Department of Public Health needs to be notified when the exposed patient's treatment cannot be deferred or controlled with pharmacotherapy.[10]

 Conclusion



EVD has emerged as a significant global public health menace due to multiple disease outbreaks in the last 25 years. Recent advancements are being carried out in the form of effective Ebola virus vaccine and anti-Ebola virus drugs. However, rapid geographic dissemination, nonspecific clinical presentation, lack of vaccine, and specific diagnostic test are the possible challenges to combat this dreaded public health menace.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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