“There is nothing so patient, in this world or any other, as a virus searching for a host” – Mira Grant, Countdown (Newflesh Trilogy,#0.5)
“You have to love its simplicity. It’s one-billionth our size. And it’s kicking our butts” – Dustin Hoffman, Outbreak
In Laurie Garrett’s sentinel books, The Coming Plague: Newly Emerging Diseases in a World Out of Balance, and Betrayal in Trust: The Collapse of Global Public Health, the author brilliantly recalls the front-line battles against killer plagues, while providing a clarion call to warn the “global village” regarding the evolution of emerging infectious diseases and the inadequacies and omissions of our global public health infrastructure. Our recent experiences with emerging infectious diseases (EIDs), such as Zika virus infection, Ebola hemorrhagic fever, Chikungunya and dengue fever serve to solidify Garrett’s scientific and public health premise and call for global action.
The classic epidemiological triad involves host, agent and environment. The changing nature of infectious disease epidemiology is due to profound perturbations between hosts (humans/animals), microbial agents and the environment, including vectors, such as mosquitoes. The notorious vector involved with the transmission and spread of the Zika virus is the old nemesis, the Aedes aegypti mosquito, which is also responsible for the geographic spread of other viruses, including chikungunya and dengue. Viruses transmitted by mosquitoes, ticks or other arthropods are known as arboviruses. An example of this is the shift in the El Nino that has resulted in a proliferation of mosquito vectors and increased incidence of vector-borne diseases, such as West Nile encephalitis, dengue fever and chikungunya and Zika virus. With human-made disturbances, such as deforestation of tropical rain forests, and complex humanitarian emergencies generated by war, conflict, and natural catastrophes, come inherent public health consequences, including incidences of exotic viral diseases.
The 138th session of the World Health Organization’s Executive Board on January 25, 2016, signaled both the “end” of the 2014 Ebola crisis and the commencement of what appears to be an even greater global public health threat, an almost ubiquitous outbreak of Zika virus infection in the Americas.
In January 2016, the US Centers for Disease Control and Prevention (CDC) advised pregnant women to refrain from travelling to countries affected by Zika, given a possible association between Zika viral infection with microcephaly, a congenital developmental abnormality denoted by a marked decrease in brain size and associated mental and neurological deficits. A neurological disorder associated with the former Swine Flu vaccination program, Guillian–Barre’, which results in muscle weakness, paralysis, and even death when the respiratory muscles become affected, has also been associated with Zika viral infection. (Petersen EE, Staples JE ,Meaney –Delman D,et al. Interim guidelines for pregnant women during a Zika virus outbreak-United States, 2016.MMWR Morb Mortal Wkly Rep 2016;65:30-33.)
The tragic implications of a devastating birth defect such as microcephaly for global maternal-child health are profound. While the evidence is definitely not conclusive by any means, the possibility of adverse fetal outcomes remains a strong possibility, therefore in the spheres of public health preparedness and responses, authorities must err on the side of safety and precaution. The associated microcephaly and neuropathy has prompted WHO’s International Health Regulations Emergency Committee to declare a Public Health Emergency of International Concern.
What does this all mean for mass gathering events such as the 2016 summer Olympic Games, followed by the Paralympic Games, as well as the Rio Carnival in Brazil, both totaling to well over 2 million visitors alone? Or the estimated 7 million plus pilgrims expected to be hosted by Saudi Arabia from 180 countries for the Umrah and the Hajj, which receives thousands of Latin Americans annually? There will be challenges to bio-surveillance in Brazil, for example, where viral spread is extensive , and identification of new cases may become difficult due to this factor, and in other areas of the world such as Saudi Arabia, mosquito populations will be denser due to higher temperatures expected in the northern hemisphere. Sexual transmission of the Zika virus has also rung some global alarms, especially among vulnerable populations such as commercial sex workers and those that practice unprotected sex.
The epidemiological interplay of host-agent-environment/vector in the above venues can lead to an even greater bio-epidemiological emergency involving Zika and other arboviruses, as dengue and chickungunya have followed similar geographical patterns and are expressed by the same vector. Prudent public health practices such as public health education, vector control measures, such as mosquito eradication programs, personal protection strategies such as insect repellant mosquito nets, protective clothing, and the use of air conditioning in residential structures to maintain cooler temperatures to discourage larvae hatching will do much to decrease viral transmission and associated morbidity and mortality from arbovirus diseases.
The global experience with viral threats continue to remain in our future. We will continue to face the possibility of pandemic influenza from highly virulent strains, e.g. H1N1, and other viral foes such as the coronaviruses (SARS, MERS), viral hemorrhagic illnesses caused by Filoviruses, (Ebola and Marburg), and of course, the vector-borne diseases caused by the arboviruses, such as the Zika and chikungunya viruses.
While the viral threats which can overwhelm health care delivery systems, public health infrastructure and shred our societal fabric and its various components continue to loom, they should serve as a firm reminder that we are not an invincible species, and that we must remain ever so vigilant and prepared for the worst-case scenario.
The non-conventional threat of biowarfare, bioterrorism or biosafety containment failure featuring emerging pathogens, should also not be discounted. The seeds of annihilation do not always lay within the core of a thermonuclear weapon, but may very well grow on an obscure tissue culture.
The Nobel Prize laureate, microbial geneticist and bio-preparedness expert, Joshua Lederberg, Ph.D., perhaps said it the best when he noted ”Nature is not benign. Mankind ‘s survival is not a pre-ordained evolutionary guarantee”.