Background

Africa is one of seven continents and is the second largest in population falling short only to Asia. It has subtropical and tropical terrain and climate which is the ideal habitat for many animals and other organisms. Unfortunately, this leads to more potential infectious diseases coming into human populations through zoonotic transmission (CDC.gov). This transmission has birthed the relatively new - but extremely deadly - Ebola virus.

Ebola belongs to the Filoviridae virus family (CDC.org). Ebola virus disease (EVD), formerly known as Ebola hemorrhagic fever, is a fatal emerging disease that results from infection by the Ebola virus. The first epidemic of the disease occurred in the Democratic Republic of Congo in 1976 near the Ebola River (CDC.org). The second outbreak occurred in that same year about 500 miles away in South Sudan (CDC.org). Right now, EVD is endemic to countries in Africa; however, it poses a global threat. It is estimated that 11,000 deaths have occurred since its first discovery in 1976 (Herrera et al., 2018). The mortality rate ranges from 25% to 90%, with the average being at about 50% (Who.int). Although EVD is rare, it doesn’t seem to show any bias in which people it infects. The destructive nature of the virus has led the United Nations Security Council to pass Resolution 2177 in September of 2014 which states Ebola threatens world peace (Wojda et al., 2015). EVD continues to plague Africa with epidemics that have risen as recently as 2019. This paper will explore the pervasiveness of Ebolavirus, examine its impact on environmental and sociocultural factors, and examine various challenges with vaccine development.

EVD is a rare disease but continues to plague Africa. There are currently five known species of Ebola virus: Bundibugyo, Zaire, Sudan, Cote d’Ivoire (Tai Forest) and Reston ebolaviruses. Other than the Reston ebolavirus, all can cause illness and be fatal to humans and several non-human primates (CDC.gov). Those who are infected often begin to show mild symptoms of fever, severe headache, muscle pain, weakness, and fatigue after a 2 to 21 day incubation period (CDC.org). More severe symptoms occur as the disease advances and include vomiting, diarrhea, rash, symptoms of kidney and liver failure, and internal and external bleeding (Who.int). Ebolavirus doesn’t seem to show any bias in who it infects making it a true pathogen. Thus far the highest fatality rates have been seen in those infected under the age of 5 and over the age of 45 (Wojda et al., 2015). There is a need for better understanding of this virus, and many steps need to be taken in order to avoid a pandemic.

To understand the nature of EVD, it is imperative to understand the history of the disease. Initially, the first outbreaks in 1976 were thought to be isolated incidences where an individual who was sick travelled from Zaire, now known as the Democratic Republic of Congo, to South Sudan, carrying the virus (CDC.gov). Scientists later discovered this was not the case. It was later discovered the two outbreaks were actually caused by two different strains of the Ebola virus, now known as the Zaire ebolavirus and Sudan ebolavirus (CDC.gov). The origins of the virus are still uncertain. Spillover of the virus into humans is believed to have occurred by either the consumption of bushmeat (considered a delicacy in Africa) or from fruit bats (Das et al., 2015). Fruit bats belonging to the Pteropodidae family are thought to be the natural hosts of the virus, and spillover could have taken place as a result of direct contact with the bats, or indirect contact with bat excretions or secretions (Das et al., 2015). Although the earliest recorded epidemics of the disease occurred in 1976, it is believed there were more cases in history that are still unknown.

Ebola: The successful pathogen

There are many characteristics that make the Ebola virus an extremely successful pathogen. As there are five different species of the Ebola virus, four of which causes fatal disease in humans, the genetic diversity or the virus contributes to it being a successful pathogen as it increases the difficulty for testing for the virus and effectively manufacturing a vaccine to treat the different species of Ebola (Leendertz et al., 2016). The virulent nature of Ebola is a major contributor to its success as well. Ebola infects the human body faster than the immune system can respond in most cases (livescience.com, 2019). As mentioned previously, Ebola also shows no bias in the age, gender, and ethnicity of individuals it infects. This gives Ebola an edge as a pathogen being able to infect, survive, and spread using humans as hosts.

Only those who are symptomatic of the disease are capable of spreading it (CDC.gov); however, EVD is highly communicable. The various modes of transmission of Ebola are another major contributor to its effectiveness as a pathogen and to why it is so threatening on a global scale. It can transfer human to human through direct contact; the virus can spread by contact with the blood, or with other bodily fluids of an infected individual, whether they are alive or dead (Tiffany et al., 2017). The Ebola virus can also be spread through contaminated needles and syringes (CDC.gov). Fischer et al. (2015) experimentally determined that the Ebola virus can survive for up to nearly 15 days on the most common surfaces found in hospital settings in Africa. This allows for nosocomial transmission and allows the pathogen to spread easily if proper sterilization procedures are not used. This ability to survive on surfaces for multiple days without a host makes Ebola extremely dangerous and contributes to its pervasiveness.

The Ebola virus can also be sexually transmitted through semen (Das et al., 2015). This transference is particularly important as the Ebola virus is capable of surviving even after the patient is no longer symptomatic and has recovered from EVD (Wojda et al., 2015). There are asymptomatic individuals who are carriers of the deadly virus but are thus far believed by many people to not be infectious (Herrera et al., 2018). Ebola is not known to use food as a vehicle for transmission; however, it is possible that people who handle or consume bushmeat may become infected (Das et al., 2015). The ability of Ebola to be transmitted with ease, and its incredible ability to survive on surfaces without a host, make Ebola an extremely dangerous and strong pathogen. Knowing the multiple pathways that Ebola can infect an individual is critical to making appropriate plans to combat future outbreaks.

Environmental Factors

Africa is home to many infectious diseases, and the subtropical terrain and climate, deforestation, and urbanization contribute to the continent being an ideal environment for many pathogens. Much of Africa is subtropical; this allows for animals and humans to live in close proximity to each other (CDC.gov). The subtropical climate is also ideal for the survival of many animals such as fruit bats, chimpanzees, gorillas, duikers, rodents, and many others. These animals also happen to be either known reservoirs, or suspected reservoirs, to the Ebola virus (Judson et al., 2016). The ideal climate and terrain for these animals inadvertently makes the Ebola virus more prevalent as the virus needs hosts for extended survival and these animals make ideal hosts. Having a large amount of animal reservoirs for the virus allows for spillover events to occur.

The subtropical terrain and climate of Africa may be ideal for the survival of the animals the Ebola virus uses as hosts, but this does not mean that climactic factors are a major contributor to the survival of the virus itself. Although climactic factors contribute to the survival of the Ebola virus, various conditions, such as temperature and rain, do not seem to significantly contribute to the spreading of the disease through spillover events. A study conducted by Judson et al. (2016) concluded there was no statistically significant difference in spillover events between the Ebolavirus strain and the Sudan ebolavirus strain when it came to temperature and rainfall. This alludes to the fact the climactic factors are primarily involved indirectly with the survival of the Ebola virus. In general, the subtropical temperatures of Africa are ideal for viruses and bacteria to grow in, but temperatures, as well as levels of rainfall, are not significant in determining potential future outbreaks.

The terrain of Africa also plays a significant role in spillover events occurring. A study conducted by Judsen et al. (2016) showed a positive correlation between the Ebolavirus strain and evergreen broadleaf forests. This same study also showed a positive correlation between the Sudan ebolavirus strain and woodlands in more elevated areas of Africa (Judson et al., 2016). Ultimately, the climate in Africa provides a zoonotic niche for the Ebola virus (Buceta and Johnson, 2017). The climate in Africa is ideal for fruit bats which are the major reservoir for the Ebola virus (Buceta and Johnson, 2017). Again, this emphasized the point in which Africa’s climate inadvertently contributes to the prevalence of the Ebola virus in Africa. 

Conversely, although Africa’s terrain and climate play an inadvertent role in the prevalence of the Ebola virus, deforestation and urbanization contribute directly to the spread of the virus. Deforestation has led to people living in closer proximities to animals. As the environment changes, animals naturally tend to adapt to these environmental changes. This poses a major threat as roughly 75% of emerging infectious diseases are caused by zoonotic transmission (Buceta and Johnson, 2017). As humans begin to live in close quarters with animals, many of the same food sources are shared, including fruits and vegetables. Unfortunately, any fruit or vegetable that ends up with secretions or fluids containing the Ebola virus from its various hosts becomes unsafe to eat without risk of infection.

Urbanization is a major contributor to the spread of the Ebola virus. Not only does urbanization lead to animals and humans living within close proximity to each other, it has allowed for ease of travel for human hosts of Ebola. With road construction and travel made easier through urbanization, infected humans are able to travel with ease and bring Ebola to areas in which the Ebola virus disease is not currently endemic (Ratnapradipa, 2015). Urbanization also means building new buildings. These new buildings create new surfaces in which the Ebola virus can survive on for several days within fluids. Common building materials used and found in buildings in Africa include stainless steel, plastic, and Tyvek. A study conducted by Fischer et al. (2015) concluded that the Ebola virus can survive on these surfaces from about seven days to nearly fifteen days.

As it has been shown, there are many factors that contribute to the survival and spread of the Ebola virus, and the subtropical terrain and climate, deforestation, and urbanization in Africa are only a few examples.

Sociocultural Factors

There are many sociocultural factors in Africa which Ebola has affected and been effected by. Burial practices and social stigma of hospitals continue to allow for Ebola to thrive in Africa. The indigenous people of Africa are very family oriented and when family members pass away there are certain burial traditions conducted by the deceased’s living relatives. This includes the removal of bodily fluids of the deceased and handling of his or her body (Adongo et al., 2016). Unfortunately, those who have passed away from Ebola virus disease are still contagious (Das et al., 2015). Without proper sterilization and care taken during burials, Ebola is capable of moving from the dead host to infect a new host. Prevalence of unsafe burial practices has led to further spread of the pathogen in this manor, leading to many secondary Ebola cases and continued outbreaks (Tiffany et al., 2017).

Upon noticing the continued outbreaks caused by secondary Ebola infections, measures have been taken in educating the people of Africa in safe burial practices. The Red Cross responded to this urgent need for safe burial practices through the implementation of safe and dignified burials (Tiffany et al., 2017). These safe burial practices require open communication between the indigenous people of Africa and those who are there to aid them. A study conducted by Tiffany et al. (2017) shows that through the use of the safe and dignified burial program, the epidemic of Ebola in West Africa alone can be reduced anywhere from 4.9% to 36.5%. This is a population range of roughly of 1,411 to 10,452 secondary Ebola cases that can be averted (Tiffany et al., 2017). In order for this projection to become a reality not only in West Africa, but for the entire continent, continued education in safe burial practices with oversight is absolutely crucial.

Practicing safe and dignified burial practices is only a steppingstone towards eliminating Ebola in Africa. A major contributor to the continued spread of the disease and virus is the social stigma of health care facilities in Africa. In many places in Africa it is believed that the hospital is a place in which you go to die. Unfortunately, this belief and stigma about hospitals has resulted in underreporting and many non-hospitalized Ebola related cases and deaths (Dalziel et al., 2018). A study conducted by Dalziel et al. (2018) found that out of 6,491 individual burials in Sierra Leone during Oct 17, 2014 and April 3, 2015, only 4,020 of the deceased had laboratory testing done for Ebola. This leaves almost 40% of those who passed away during that specific time period of the Ebola outbreak as unknown (Dalziel et al., 2018). This underreporting can drastically impact the data on Ebola as none of these cases are included into the data collected on Ebola. This also alludes to the fact there were potentially secondary Ebola infections occurring as those who passed away were never tested for Ebola and unsafe burial practices may have been conducted. Data is essential for monitoring, and missing data can lead to severely underestimating the prevalence and severity of a disease.

Not only does underreporting increase  the inaccuracy of recorded numbers on secondary Ebola cases, but it also increases the difficulty in monitoring the disease. Those infected with the Ebola virus continue to spread it without knowledge as many people in Africa avoid hospitals and continue to use more traditional healing methods such as going to witch doctors (Wojda et al., 2015). This lack of trust between the people of Africa and hospitals is a barrier that needs to be overcome if there is to be any hope of eliminating Ebola in Africa.

Vaccine Development

There are many challenges when it comes to vaccine development. The mode of delivering, the dosage, in-vitro testing, in-vivo testing, safety, efficacy, and proper animal models are just a few of the hurdles researchers must overcome when developing a vaccine. It is also imperative the vaccines developed are unique to each strain of a virus. This provides researchers the option to either take a monovalent approach towards vaccine development or a multivalent approach. Economic considerations must take place as well, as many people residing in Africa are much poorer than those in first world countries such as the United States. All of the challenges listed above need to be taken into consideration for the effective synthesis of a vaccine for the Ebola virus.

There is currently no known vaccine or antiviral for the Ebola virus. If there is to be any fighting chance in the eradication of EVD, an effective vaccine and treatment is absolutely crucial. There have been numerous efforts and studies conducted in effectively synthesizing a vaccine. There are many difficulties to overcome in vaccine development. As previously stated, there are five known strains of the Ebola virus, four of which cause fatal disease in humans. Effectively synthesizing a vaccine that can counter this genetic variability continues to be a challenge. Current “treatments” for EVD consist of early detection, and pumping fluids and electrolytes into infected individuals (Milligan et al., 2016). Treatments is placed in quotes as the measures taken are not very effective and the primary contributor for most recoveries from EVD is the individuals’ immunogenic response (Milligan et al., 2016).

Although there are promising clinical trials utilizing various treatment options and vaccinations, there is still no official vaccine. Current animal models have shown a single inoculation of vector vaccines do provide an immunogenic response, and a more recent clinical trial has shown a heterologous prime and boost sequence using two different vector vaccines may prove to be effective in the fight against Ebola (Milligan et al., 2016). Although the results from the phase one clinical studies done by Milligan et al. prove to promising, there need to be further studies done on alternative methods to developing a vaccine.

A study conducted by Herrera et al. (2018) found individuals who carried the Ebola virus but were asymptomatic of EVD. This implies that some individuals  may have a natural immunity to the virus, and further studies need to be conducted to study those who have the virus but are asymptomatic (Herrera et al., 2018). Theses implications not only provide hope for a successful synthesis of a vaccine for Ebola, but provide an alternative source to study. Looking at the immune system and immune responses of these individuals is a necessary study and step needed to be taken in the further development of vaccines for Ebola.

Conclusion

Ebola continues to plague Africa, claiming countless lives. The pervasiveness of the Ebola virus as a pathogen has proven to provide challenges to those researching the disease. Ebola’s genetic variability, various modes of transmission, and its fatality rate all contribute to Ebola not only being a threat to Africa, but the entire world. There are many variables that aid in the spreading of the Ebola virus and these include environmental factors, sociocultural factors, and difficulties with vaccine development. Continued monitoring and tracking of the spread of the virus is essential in avoiding future outbreaks. By understanding the environmental factors which contribute to the spread of the Ebola virus, it will be  easier to track of the spread of the disease. The continued program of safe and burial practices is absolutely crucial, along with building trust and eliminating the social stigma placed on health care facilities in Africa. Education of the public on these various environmental and sociocultural contributors to Ebola is a necessary step needed to be taken in order to aid in the elimination of the spread of the Ebola virus. These are the first steps needed to be taken as current vaccines are unavailable. Although vaccine development and clinical trials are underway, the infection rate needs to be decreased and adjustments made until a successful vaccination is developed for the Ebola virus.

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