Emerging infectious diseases are infectious diseases that have showed up within a population in recent years or those whose prevalence or geographic boundary is increasing exponentially or expected to rise within the next few years (1). Emerging infections can be divided into two main groups – newly emerging and re-emerging infections. Newly emerging infections can be defined as diseases that have never been identified in the human host before. Re-emerging diseases are diseases that have been known to infect humans, but persistently emerging in novel places or as drug-resistant strains, or re-emerging despite evident management or eradication (2). This essay aims to understand the dynamic relationships between microbes, human hosts, and the environment with respect to impact on emerging infections in humans. It is also important to remember that due to the complex nature of many emerging diseases, the differentiation between emerging and re-emerging diseases tend to be debatable, resulting in multiple professionals to group them into disparate categories.
The causes of disease emergence are dependent on a number of factors yet basically result from the microorganism itself interacting with a human. These exposures can be complicated and novel diseases are frequently developed from multiple determinants simultaneously or consecutively. One key example we would be focusing on would be the Ebola outbreak in West Africa in 2014. The Ebola virus disease (EVD) is a lethal zoonotic disease caused by an infection with one of the five recognised ebolavirus species, with the Zaire ebolavirus species being responsible for this particular epidemic (3). As of 13 May 2016, a total of 28,616 cases 11,310 deaths was reported (4), making it the largest known outbreak of Ebola.
The collapse of public health campaigns and inadequacies in public health systems adds to the dissemination of emerging diseases. One of the main reasons for the emergence of Ebola in parts of Africa is the substandard active healthcare systems where the virus happened. The nations, Guinea, Liberia, and Sierra Leone are the hardest-hit and among the poorest in the world. After decades of dispute and civil conflict, their healthcare systems are essentially obliterated or significantly weakened and, in some regions, leaving behind a generation of uneducated young people. Restricted trained medical workforce, substandard facilities and equipment, incompetent administration and financing for the healthcare industry all leads to the accelerated spread (5). Healthcare professionals of Ebola patients are at utmost danger of contracting it as they are considerably more likely to be in near proximity with infected blood or body fluids. The elevated mortality rate of health practitioners in this outbreak has damaging repercussions that further delay infection control. It exhausts one of the most indispensable assets during any infection outbreak control. In the three worst-affected countries, WHO approximates that only one to two physicians are accessible to care for 100,000 people, and they tend to be heavily concentrated in bigger towns (6). Quarantine areas and hospital promptness for control measures are basically non-existent. Contact tracing of ill persons are being executed but not diligently quarantined for supervision. At the beginning of the Ebola epidemic, limited capacity to rapidly distinguish alleged cases, confirm diagnoses and implementing preventative measures led to pervasive spread (7). By the time outbreak control was attained, there were already extensive and devastating effects on Ebola patients and their families, as well as the countries’ health and financial systems (8) and population health (9).
Sociocultural actions that contradict disease outbreak regulations also play a role in emerging diseases. The predominant acceptance of particular long-established and spiritual rituals among West African populations had huge adverse impacts on the dissemination of Ebola. In Guinea, 60% of incidents have been associated with customary funerals. One of the most frequently carried out burial customs, which notably aided the dissemination of Ebola, is the rinsing and bathing of the corpse. Another stated funeral tradition is that of the family of the deceased touching the face of the corpse in what is understood as a ‘love touch’ that reinforces harmony between the living and their ancestors (10) and then proceeding to clean their hands in a shared washbasin. Given that the primary method of human-to-human transmission of the Ebola virus is through direct contact with infected body secretions as constantly described in the Ebola epidemic, the funeral and burial rituals mentioned before indirectly leads to dissemination of the disease (11). Fear causes individuals who have had contact with infected persons to evade supervision, families to conceal symptomatic relatives or bring them to indigenous doctors, and patients to escape from medical facilities. Fear and the aggression that can follow have jeopardised the safety of domestic and global medical emergency units. The fact that Ebola is often lethal and incurable further promotes alarm and continuation of these risky actions, highlighting the significance of needing medical anthropologists on the medical emergency units. This established that solely using scientific techniques without an all-inclusive regard for other circumstantial elements is not enough to regulate disease outbreak. Control measures must operate within the customs, not against it (12).
In an ever more integrated and connected world, the spreading of infectious diseases through global travel and trade is much simpler. West Africa is exemplified by a large scale of migration across extremely unregulated geographical boundaries (13), with new findings approximating that migration in these countries is seven times higher than other places globally. A huge proportion of the population in these nations do not have stable and waged jobs. Their pursuits to seek employment leads to ever-changing migration across these unchecked geographical boundaries. Migration produced two major obstacles. Firstly, cross-border contact tracing is challenging. People promptly migrate to other countries, but medical emergency units do not. Secondly, patients from bordering nations looking for vacant treatment beds are drawn to nations that are progressing in outbreak control, hence inciting transmission chains. The customary practice of returning, frequently over extensive distances, to a local village to lay to rest alongside ancestors is an alternative aspect of migration that involves an exceptionally huge dissemination threat. The epidemic in West Africa has caused fear and also infection miles away in the United States and Spain. Briefly, local threats now have global ramifications (14).
Climate change and global warming is progressively becoming a global issue as well as playing a part in the rise of infectious diseases. As Earth’s temperature rises and environments change, diseases can disseminate into novel geographical regions. A few research papers have stated the effect of global warming and climate change on the African Ebola epidemic (15) and the migratory patterns of fruit bats (16). Colonies of fruit bats migrate to regions where ecological settings are more advantageous for survival due to diminished rainfall, warmer climate and land degradation in their ecological niches in the tropical rainforest. During times of low fruit abundance in tropical rainforest, huge numbers of fruit bats travel extensive lengths to exploit fruit availability in other areas (17), with stop-overs offering a rare chance for natives to vastly hunt bats. Hunting these bats puts them at a bigger threat of zoonotic infections. Molecular examination has shown that the biological pathogen responsible for the West African epidemic diverged from the Central African ZEBOV strain about ten years ago (18). Likewise, antibodies against ZEBOV have been identified in migratory bats in faraway regions, such as Bangladesh (19) and Ghana (20), suggesting the possibility of Central African migratory fruit bats to spread the virus into other regions. Evidently, the impacts of global warming and climate change on fruit bats’ migratory patterns, from their ecological niches in the tropical rainforest of Central Africa to other faraway regions, may have potential international health outcomes. Certainly, it is a concerning world issue that vector-borne diseases, particularly mosquito-borne diseases, may produce an extensive span of emerging infectious diseases in time to come.
Numerous viruses demonstrated a high mutation rate and can quickly evolve to produce novel variants (21). Influenza viruses are useful examples of emerging and re-emerging infectious pathogens in their ability to quickly evolve following changes in host and environmental conditions via various genetic pathways. Influenza virus is recognised for its competency in altering its genetic material. There are two types of genetic mutations in Influenza A virus. Firstly, a genetic drift refers to a point mutation resulting in a slight alteration of surface antigens, producing a new variant of the same virus which leads to periodic influenza infections. Secondly, a genetic shift refers to genetic segments being translocated among Influenza A viruses from distinct species (e.g. human, birds and pigs), producing an entirely novel strain (22). Huge alterations of the influenza virus can lead to pandemics as the human immune system is not ready to identify and guard against the novel strain (23). Moreover, influenza viruses can evolve and persist for years via various genetic pathways in response to evading constant human immune pressures. Over the past decades, the 1918 influenza pandemic virus have constantly evolved via antigenic drift, reassortment between the same subtype and antigenic shift, with the latter yielding new strains in the 1957 Asian flu and 1968 Hongkong flu (24). Additionally, the 2009 flu pandemic involving the genetically complex H1N1 influenza virus is a descendant of the 1918 Spanish flu virus (24). By comparing Figure 1 and Figure 2, the emergence of multiple new variants of Influenza virus can be seen within a short time span of 4 years. The ever-changing genetic material of influenza viruses drives us to research and develop new influenza vaccines containing new antigens annually.
Whilst the world population grows and expands into new locations, the likelihood of people coming into close contact with animal species that are possible hosts of a transmittable pathogen increases. In combination with rises in population density and migration, it is evident that this presents a significant risk to population health. The 2009 Influenza A H1N1 strain was due to genetic reassortment from three distinct species: one genetic segment from human Influenza A H3N2, two segments from avian Influenza A H1N1 and five segments from swine H1N1 (25). The likelihoods of significant genetic mutations happening and then transmitted to humans are higher when humans live near to farmed animals such as chickens, ducks, and pigs. These animals are usual hosts of influenza virus, providing opportunities for the combination of different strains to produce new variants of influenza that have not emerged before. Avian H5N1 influenza, which appeared more than ten years ago, has been restricted to comparatively uncommon occurrences of the disease in humans who were in direct contact with infected birds. The H5N1 virus is extremely lethal with the majority of cases being fatal, although it has yet to develop transmissibility to humans. On the contrary, the 2009 H1N1 influenza, which was introduced into humans from pigs, was highly transmissible between humans. The H1N1 virus spread globally rapidly due to human mobility, especially air travel. Fortunately, the H1N1 virus was not as lethal as the H5N1 virus. The emergence of an influenza virus that is as lethal as the avian H5N1 virus and as contagious as the swine H1N1 virus would pose a substantial risk to global population health.
Even as eliminating particular infectious diseases and to considerably regulate many others become extremely achievable, it appears implausible that we will eradicate the majority of emerging infectious diseases in the near future. Disease-causing pathogens are capable of rapid genetic mutations, resulting in novel phenotypic characteristics that exploit the host and environment. Meanwhile, novel human diseases keep surfacing. Epidemics still draw international awareness and need considerable global cohesion to control and regulate, whether or not they become more prevalent. With uncompromising alertness, current focused investigation, and quick advancement and implementation of several measures to counteract the threat such as monitoring means, diagnostics, drugs, and vaccines, we can overcome pathogenic advantages. In this period of time, there are various significant emerging, re-emerging, and unchanging infectious diseases are becoming more in check. Nonetheless, the triumph of preventing the numerous novel emerging diseases that will definitely emerge is uncertain. Even though we have countless means to tackle diseases, including readiness strategies and hoards of medicines and vaccines, every novel disease brings a set of different challenges, pushing us to constantly change together with the ever-changing threats. The fight against emerging infectious diseases is always ongoing; success does not imply eradicating every single disease but instead being ready in advance of subsequent ones.
...(download the rest of the essay above)