“And I looked, and behold a pale horse! And its rider’s name was Death…to kill with sword and famine and pestilence”…Revelations 6: 8
“However secure and well-regulated civilized life may become, bacteria, protozoa, viruses, inflected fleas, land stalk us in the bodies of rats, mice, ticks, mosquitoes, and bedbugs will always lurk in the shadows ready to pounce when neglect, poverty, famine, or war lets down the defenses. And even in normal times they prey on the weak, the very young, and the very old, living along with us, in mysterious obscurity waiting their opportunities. About the only genuine sporting proposition that remains unimpaired by the relentless domestication of a once free –living human species is the war against these ferocious little creatures, which lurk in the dark corners and stalk us in the bodies of rats, mice, and all kinds of domestic animals; which fly and crawl with the insects, and waylay us in our food and drink and even in our love” – Hans Zinsser, Rats, Lice and History, 1934
While the morbidity and mortality from infectious diseases has declined dramatically since the 1900s due to improvements in sanitation and the development of effective vaccines, antibiotics and antiviral agents, novel and emerging microbial agents with increased virulence and infectivity continue to pose a threat to global health security.
Novel and emerging infectious diseases are those that are: (1) newly recognized as occurring in humans, animals or plants, (2) newly occurring in a different population than previously, (3) affecting greater numbers of individuals, or, (4) evolving new attributes (e.g., resistance or virulence).
In a 2008 study funded by the National Science Foundation (NSF), about two-thirds of emerging infections were found to be zoonotic (animal in origin) and the majority of those came from wild animals (e.g. SARS). As with any public health problem, expeditious and official recognition of novel and emerging infectious diseases is essential. When public health officials and the health care community take ownership of the serious nature of these bio-threats, only then can communities and stakeholders formulate effective plans.
Bio-preparedness is actually a reciprocal function for both bioterrorism (BT) related events and naturally-occurring outbreaks. If it is possible to plan and prepare for an epidemic or pandemic event, the same principles and strategies can be applied to acts of bioterrorism.
The factors that contribute to the emergence of novel pathogens can be counted as factors which can foster and exacerbate the virulence, pathogenicity and transmission of an intentionally disseminated microbial threat.
While factors influencing the balance between pathogens and host are always unique, some common denominators usually fit into the overall equation.
Population growth has been one of the most important factors related to the emergence and propagation of both older and novel microbial threats. Urbanization and concentration of the labor force, with industrialization has led to overcrowding and inadequate infrastructure to accommodate expanding populations. Namely, sewage disposal, water supply, pest control, and food storage and distribution have not kept up with the burgeoning populations of the developed and developing world. The association of infectious diseases with sub-standard living conditions in slum dwellings, for example, is well documented, and remains a challenging problem to this very day in many parts of the globe, including the Western world.
Speed and ease of travel by aircraft makes it possible to expeditiously arrive from an endemic area of the world in Africa or South America to anywhere in the world within the incubation period of certain viral hemorrhagic fevers such as Lassa fever or dengue. One of the best models for infectious spread of a novel pathogen by airline travel was the Severe Acute Respiratory Syndrome (SARS) pandemic that affected 8,450 persons and caused 850 deaths in 26 countries on 5 continents in 2003 before it was controlled. Also, air travel facilitates the spread of novel strains of influenza, including highly pathogenic variants.
Changes in the Food Industry: The global food supply can also be a source of disease transmission. Changes in how food is grown processed, stored and delivered globally can impact and facilitate the growth, mutation rate and infectivity of emerging infectious diseases. Changes in global markets and the speed of transportation have made it economically profitable to transport food between the hemispheres-for example, enabling the U.S. consumer to have fresh fruits and vegetables on a year-round basis. The rise of agribusiness has also created agricultural empires which maximize productivity often at the expense of biosafety and biosecurity, despite the notion that they have safer practices. An example of this is hybrid agricultural practices allowing different species to essentially co-mingle and creating optimal reservoirs for the evolution and transmission of novel infectious diseases, such as newer highly pathogenic strains of influenza created due genetic re-assortment and trans-species jumps.
Proper hygienic practices on farms are too difficult to maintain due to the reliance on migrant farm workers who may be carriers of pathogens from other countries, and who may not have proper sanitary facilities to use or be able to obtain preventive health services.
Antibiotic Use and Abuse: The use and over usage of antimicrobial agents is a definitive
cause of the emergence of resistant pathogenic microorganisms. In the last few decades, Methicillin-Resistant Stapylococcal Aureus (MRSA) organisms have emerged and thrived as the Gram-positive organisms that are most frequently responsible for invasive bacterial infections among hospitalized patients and those infected in the community in the United States. Some of these MRSA infections are responsible for significant morbidity and mortality.
Among other major factors responsible for the current and future evolving biological crisis are expansion of human populations into previously uninhabited areas which harbor highly pathogenic microorganisms, including some of the world’s dreaded emerging infectious diseases, such as the viral hemorrhagic fevers Lassa and Ebola caused by Filoviruses, Monkeypox, an Orthopox virus cousin related to the feared smallpox (Variola major) and HIV-1 and HIV-2 infections. These and other infections such as Lyme disease (Borrelia burgdorferi) and Rocky Mountain spotted fever (RMSF) are related to the encroachment of human populations into wilderness areas and increased exposure of humans to zoonotic pathogens.
War and societal disruption often result in rampant and evolving infectious diseases involving both military combatants and non-combatants in war and strife –torn regions of the world.
Still other contributing factors are as diverse and complex as climate change, decreased immunocompetence due either to non-immunized populations, HIV/AIDS-related illness or immunosuppressive therapies utilizing antineoplastic drugs, radiotherapy or other immunological disorders and biological response modifiers (BRMs).
We can plainly elucidate what these various factors and co-factors may mean to the initiation and propagation of a naturally–occurring epidemic or pandemic event, however, the interplay of causative or contributing nuances such as air travel, compromised immune systems, societal and infrastructure disruption and/or urban overcrowding can be prime determinants in biological warfare or bioterrorism-related events and their survivability.
The use of novel and emerging infectious microbial agents in the realm of biowarfare or bioterror have been addressed and debated in several respected global venues. The spectre of biowarfare and bioterrorism has become more complex because of increased bio-agent variations, sophistication, and the feasibility of in vitro genetic modification. It is possible, even probable, that microbial agents could become unleashed upon the world that have enhanced virulence, superb environmental viability, special resistance to multiple medical countermeasures, such as antimicrobials, anti-viral compounds and vaccines, fool, and defeat even the most sophisticated array of filtration systems and bio-detection technologies.
The use of synthetic biological and genetic engineering/biotechnology can lead to sophisticated constructs and chimeric organisms with the ability to express a broad spectrum of disease and evade diagnostics and agent characterization.
Can a flea, mosquito or other vector be used as a weapons delivery system for some biological agents? The answer is, at once, both sobering and not surprising, as these are natural vectors for many emerging infectious diseases, including the most recent and dreaded microbial threat: Zika virus.
While effective aerosolization, pulmonary deposition and retention of respirable, micron-size, infective particles is a prime way of delivering an infective dose (ID) in biowarfare, the ubiquitous presence of insect vectors and the effective transmission of both human and non-human animal infectious diseases by them constitutes a viable and low-tech dissemination methodology for emerging infectious diseases as bioweapons. Therefore, the threat of emerging infectious agents being used to infect susceptible populations, the elderly, the very young, the immunocompromised becomes even more realistic by the deployable delivery devices that can be bred specifically to deliver their infective payloads.
The threat of novel and emerging infectious diseases is real and their nefarious use as deployable bioweapons may have become within the reach of a mosquito’s or flea’s bite. The living scourges of naturally-occurring epidemics, pandemics and bioterror continues to encroach upon humankind. The emergence of novel pathogens and the consequences of their impact upon society, may very well become the defining components of our very own survival.