Epistemology of Ebola Virus Disease (EVD)

Introduction

The Zaire Ebola virus is amongst the most contagious pathogens among the disease-causing hemorrhagic fevers, with reported case fatality rates of approximately 90%. EVD causes severe bleeding complications and multi-organ failure resulting in death. By October 2014, the World Health Organization (WHO) had reported 5335 cases of EVD (probable, suspected, and verified) with 2622 fatalities, producing a case mortality rate of approximately 50% (Wang et al., 2015). Therefore, this paper aims to give an epidemiological overview of EVD, emphasizing clinical manifestations, development of this disease, social determinants of the disease, pathogenesis, and treatment options. The paper also reviews the role of the community health nurse and why demographic data are necessary for the health of the community.

Description of the Ebola Virus Disease (EBV)

Ebola virus disease (EVD) is a Filovirus, which means it is an encased RNA virus comprising eight genes. To date, five EVD virus strains have been identified, with three being extremely pathogenic to humans. These strains include the Bundibugyo Ebola virus (Case fatality rate (CFR) 25%), Zaire Ebola virus (CFR 70 – 90%), and Sudan Ebola virus (CFR – 50%). EVD links to the host cell through glycoproteins that activate the absorption of the virus. Although EVD has affected many areas, the most massive epidemic recorded occurred in West Africa in 2014. The 2014 outbreak was caused by the Zaire Ebola virus, which belongs to the Ebola virus species. The strain combined with the Marburg virus species to create the Filoviridae family of viruses.

EVD is a severe, infectious, viral disease affecting humans and is often deadly. Wang et al. (2015) allude that once the virus enters the human cell, it un-coats and starts duplicating the eight negative-sense RNA genes (one non-structural gene and seven structural genes). Initially, EVD targets the immune cells that respond to the area of infection in the body. Macrophages or monocytes then transmit it to the lymph nodes, followed by the spleen and the liver. Afterward, the virus spreads all over the body, creating a cytotoxic outcome in each of the infected cells.

Symptoms of EVD manifest two to twenty-one days after infection, and the victims are infectious from the start of symptoms. Den Boon et al. (2019) explain that symptoms include vomiting and nausea, fatigue, and hemorrhaging of the mucus membranes and skin. Other signs include abdominal pain, diarrhea, headache, a fever, disseminated intravascular coagulation, skin rashes, and coughing. Symptoms of the disease manifest differently from one case to another and from one strain to another: For example, during the 2014 epidemic, excessive bleeding only happened in the late stages of the disease process and in only about 18% of cases (Wang et al., 2015). On average, death occurs six to sixteen days after infection, typically due to hypotensive shock and multi-organ failure.

Chain of Infection

The epidemiologic triad model (or epidemiologic triangle) suggests that the interaction of the environment, host, and agent causes the contagious disease. More precisely, transmission happens when the agent gets out of its host or reservoir via a portal of exit and infects a vulnerable host. Such a classification is sometimes referred to as the chain of infection.

The Reservoir

An infectious agent’s reservoir is the habitat where the virus usually lives and reproduces. Reservoirs include the environment, humans, and animals and might or might not be the origin from which an agent transmits to a host. Humans are susceptible to viruses that emanate from animal reservoirs. Several of these viruses or diseases are transferred among animals, with people being secondary hosts. The term zoonosis denotes a communicable disease that is contagious under natural circumstances, from vertebrate animals to people. Several newly documented infectious diseases in humans, such as SARS and EVD, could have developed from animal hosts. In Africa, fruit bats are thought to be the main reservoir for EVD. However, transmission between bats and other animals (like monkeys) thought to carry the Ebola virus is now clear.

Portal of Exit

The term “portal of exit” refers to the path through which a pathogen exits its host. The portal of exit commonly coincides with the pathogen’s localized site. For example, Mycobacterium tuberculosis and influenza viruses exit via the respiratory tract, cholera vibrio through feces, schistosomes via urine, while Sarcoptes scabiei occurs through scabies skin lesions. EVD exits its reservoir when the bodily fluids of a sick animal come into contact with humans (normally bush meat hunters) (Campbell & Linderman, 2015). The spill-over is very small, with most of the human cases resulting from transmission among humans.

EVD Transmission

Researchers believe that fruit bats are the most common Ebola virus hosts. Den Boon et al. (2019) note that Ebola enters the human population by close interaction with the secretions, organs, blood, or other body fluids. People contract the disease when they interact closely with infected chimpanzees, fruit bats, monkeys, gorillas, or forest antelopes found dead or sick in the forest.

The term “portal of entry” describes how a pathogen enters a vulnerable host. The entry portal has to give access to tissues where a toxin can act, or the pathogen can reproduce. Infectious agents usually get into a new host using the same portal used to leave the source host. Ebola typically enters the human body via skin lesions, including droplets on mucus membranes and micro-abrasions (Houlihan et al., 2017). Afterward, people transmit the disease amongst themselves through direct contact (via mucous membranes or broken skin) with body fluids or blood of an individual who has died from the disease. Transmission can also happen if people handle items that have been contaminated with bodily fluids (such as vomit, blood, or feces) from victims or through bodies of individuals who died from the disease.

All bodily fluids such as saliva, urine, blood, breast milk, sweat, semen, diarrhea, vomit, sputum, tears, and even the skin’s oil glands contain some viral particles. Traces of Ebola still exist in semen four months after recovery from the disease. However, studies concerning the issue are inadequate. Viral particles are traceable in other bodily fluids for about fifteen days after the start of symptoms (Den Boon et al. 2019). Research indicates that viral particles last the longest in breast milk and convalescent semen. Cases of sexual transmission of EVD are rare. Based on existing evidence, the WHO recommends that EVD survivors should either refrain from all kinds of sex until their semen tests negative for the Ebola virus. These individuals can equally practice safe sex by the consistent and correct use of protection for about twelve months.

The Ebola virus is categorized as a Biosafety Level Four Pathogen as well as a Bioterrorism Agent alongside other types of viral hemorrhagic fevers. Individuals are contagious as long as their secretions and blood contain traces of the virus (Houlihan et al., 2017). Burial ceremonies where mourners come into direct contact deceased person’s body can also lead to the transmission of the Ebola virus. There have been notable cases where healthcare workers in affected regions have contracted the disease after close contact with EVD victims, especially when they compromise infection control procedures. Samples from sick individuals are contagious. Therefore, testing should take place under suitable biological containment conditions. Each material touched by an infected individual, body fluids, used PPE, and medical need proper disposal and destruction and treatment as infectious medical waste. Non-disposable items such as building structures, furniture, and rubber boots require professional disinfection.

Diagnosis

Diagnosis of EVD is made through using the following diagnostic techniques:

• Antigen-capture detection tests.
• Electron microscopy.
• Virus isolation through cell culture.
• Reverse transcriptase-polymerase chain reaction assay
• Serum neutralization test.
• Antibody-capture enzyme-linked immunosorbent assay

Careful thought is essential when selecting the most appropriate diagnostic tests. Factors to consider include disease prevalence and incidence, technical specifications, and medical and social consequences of test results. Scholars recommend the prioritization of diagnostic tests internationally and independently evaluated.

The Ebola virus is usually traceable forty-eight hours after infection in both non-lethal and fatal cases. Such observation suggests that negative test results in the initial forty-eight hours after contact do not rule out the possibility of an infection. Because of EVD’s swiftness, serology does not play a role in the diagnosis of acute patients. However, it might be useful for surveillance and epidemiological studies. While IgM antibodies can generally be detectable as early as two days after symptoms appear, they can vanish from one to six months (Wang et al., 2015). Typically, researchers believe that the IgG response begins between days six and eighteen after the onset of disease and remains traceable for years. The antibody profile of the sera from individuals with fatal EVD compared with those that recover is noticeably different. The difference can function as an analytical indicator for managing sick individuals because antibody reactions differ between the survivor and fatal cases. It is also evident that people who die from the disease exhibit absent or much lower antibody reaction than those who recover.

Samples collected from sick individuals are highly contagious. As such, laboratory analysis on non-inactivated samples must take place under strict biological containment conditions (Houlihan et al., 2017). The triple packaging method is useful in every biological specimen during transportation.

It can be problematic to clinically differentiate EVD from other communicable diseases like meningitis, typhoid fever, and malaria. Furthermore, several symptoms of EVD and pregnancy are quite similar. Due to threats that the virus has on expectant women, these individuals require prompt testing if there is a suspicion of EVD.

Treatment

Supportive care, especially rehydration with intravenous or oral fluids and treatment of symptoms, enhances survival. Presently, there is still no verified cure available for the disease. However, there are numerous potential treatments, including drug therapies, immune therapies, and blood products under assessment. The first multi-drug randomized control trial took effect during the 2018-2019 EVD outbreak in the Democratic Republic of Congo. Significantly, the trial focused on assessing the safety and effectiveness of experimental drugs used in the treatment of people suffering from EVD under an ethical basis formulated in consultation with specialists in the field.

Control and Prevention

The most appropriate outbreak control depends on applying a raft of interventions, comprising contact tracing, good laboratory service, surveillance, social mobilization, case management, and safe burials. Community participation and engagement is vital for effective control of outbreaks. Medical practitioners play a significant role in the community by preventing infections. Public health nurses apply many guiding principles when evaluating the community, handling their needs, and enhancing health outcomes (Campbell & Linderman, 2015). Some principles that can help in EVD control and prevention include the application of the social-ecological model (Campbell & Linderman, 2015, p. 1). The model considers “relationship interactions, the social causes of health view, societal interaction and connection, and individual biology.”

Increasing awareness of infection, as well as protective measures that people can take, is a prudent way to lessen human to human transmission. Messaging about risk reduction should focus on many factors, such as:

• Decreasing the risk of transmission between humans through close or direct contact with individuals with Ebola symptoms, especially with their body fluids.
• Wearing suitable personal protective equipment (like gloves and other PPE) when caring for sick individuals (Houlihan et al. 2017).
• Decreasing the risk of transmission from wildlife to humans by minimizing direct contact with infected animals (like fruit bats and monkeys) and cooking meat well before eating.
• Outbreak containment procedures, including dignified and safe burial of EVD fatalities, identification of individuals who might have contacted EVD victim and assessment of their health for at least 21 days (Den Boon et al. 2019).
• To contain the spread of the disease, it is essential to separate the sick from the healthy. Notably, “the Ebola virus can persist in immunologically protected body sites in survivors of EVD, producing the potential to trigger new chains of transmission” (Den Boon et al. 2019, p. 240). It is also essential to maintain a clean environment and good hygiene to contain the spread of the disease.

Descriptive Epidemiology: Spatial and Place Characteristics

In terms of geographic distribution or “place,” the EVD outbreak in West Africa (2013 – 2016) was different from earlier outbreaks in many ways. First, it occurred in ten countries that had not experienced any prior EVD illness. Among these, five countries have experienced several outbreaks since then: Uganda (five outbreaks), Gabon (four outbreaks), Republic of Congo (three outbreaks), South Sudan (three outbreaks), and the Democratic Republic of Congo (seven outbreaks). Second, the outbreak from 2013 – 2016 was the only EVD “pandemic” in history that extended globally, with cases in Africa, the United States, and Europe. However, ninety-nine percent of the cases occurred in Africa.

Third, the outbreak was different from others because the virus penetrated into densely populated, impoverished, and susceptible metropolitan centers. Earlier EVD outbreaks had been comparatively short-lived and took place in rural areas. Den Boon et al. (2019) states that “most of EDV events happened in isolation, in areas that the disease had not previously affected, or well after community transmission had ended” (p. 243). The 2013–2016 West Africa EVD pandemic grew into a firestorm owing to its viral spread. Fourth, the 2013–2016 pandemic was the only EVD outbreak where resultant cases took place due to air travel into highly-developed countries.

Public Health Response to EVD Outbreaks

Halting and containing disease transmission of the Ebola virus poses extraordinary challenges to international, regional, and local capabilities. Such challenges prompted the U.S. Centers for Disease Control and Prevention (CDC) to develop response measures to deal with localized and wide-scale outbreaks. The CDC suggests interlocking elements that need a concurrent application to curb the spread of the disease and counter any outbreak. These components include:

• Carrying out thorough community-based surveillance to isolate and spot any individual infected with the EVD.
• Applying “contact tracing” for each EVD contact and observing these people for 21 days, which constitute Ebola virus incubation period.
• Studying past and current EVD cases with trace-backs to spot ongoing “chains” of transmission.
• Maintaining daily case recording and reporting.
• Tracing deaths and using skilled burial teams to handle the remains of the dead carefully.
• Training healthcare workers on safe ways of donning, removing, and working in PPE, for the joint protection of patients and staff.
• Updating and educating healthcare workers about infection control practices. Such awareness creation in necessary to the public’s trust and their established relationships in communities. The skills enable public health nurses to combat EVD outbreaks successfully (Campbell & Linderman, 2015).

The multi-faceted approach developed by the CDC, drawing upon international, regional, and local assets, has the potential to halt the epidemic spread the EVD.

Conclusion

The vast and rapid geographic spread of past EVD outbreaks provides a reasonable basis for increased alertness and awareness of clinicians concerning the epidemiology of the disease. The initial EVD symptoms, such as fever, headache, flu-like illness, and nausea are non-specific. Besides, EVD is highly contagious when people contact infected wild animals or victims directly. Therefore, healthcare workers should have the necessary knowledge regarding the management and isolation of infected individuals. To deal with any outbreak, healthcare workers should also be conversant with the supportive care given to EVD patients. Past outbreaks (such as the 2013–2016 West Africa EVD pandemic) stress that inexperienced clinicians in affected countries can play in exacerbating the situation.

Research of EVD chain of transmission can help pinpoint effective control methods that require reinforcement and inform the optimal use of available resources. Identifying routes of the EVD transmission is not straightforward. Therefore, a thorough epidemiologic study and analysis of viral RNA sequences can offer helpful information. Since situations are very different, additional expertise is integral in understanding Ebola’s epidemiology, creating the best practices, and combating it.

References

Campbell, L., & Linderman, T. (2015). Public health nurses strive to keep community safe, healthy. The American Nurse, 47(2), 10-10.

Den Boon, S., Marston, B. J., Nyenswah, T. G., Jambai, A., Barry, M., Keita, S.,… & Green, H. H. (2019). Ebola virus infection associated with transmission from survivors. Emerging infectious diseases, 25(2), 240.

Houlihan, C. F., McGowan, C. R., Dicks, S., Baguelin, M., Moore, D. A., Mabey, D.,… & Glynn, J. R. (2017). Ebola exposure, illness experience, and Ebola antibody prevalence in international responders to the West African Ebola epidemic 2014–2016: A cross-sectional study. PLoS medicine, 14(5), 1-18.

Wang, L., Yang, G., Jia, L., Li, Z., Xie, J., Li, P.,… & Song, H. (2015). Epidemiological features and trends of Ebola virus disease in West Africa. International Journal of Infectious Diseases, 38, 52-53.