Conclusions

Introduction

We live in an age of constant change, due, to a large degree, to the continuing threat of infection by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), the causative agent of COVID-19. This recently emerged pandemic coronavirus has spread throughout the world. Countries or parts of countries have responded by locking down segments of their areas, in some cases, literally preventing the population from leaving their homes. Some other places were less stringent and only locked down places where people may gather and spread the virus. Often, this led to only “essential” services remaining open, while small and large businesses, places of worship, and fitness facilities were closed. Much of life is a trade-off: The closure of business most likely was an important factor in slowing the spread of the disease and “flattening the curve” so as to prevent hospitals from being overwhelmed. Unfortunately, the closures will most likely lead to the permanent loss of jobs and income. The effects of these lockdowns have also triggered crises in mental health, increasing depression, and, in some cases, suicide incidence. Many of our elderly population, especially those living with comorbidities, are very vulnerable to developing fatal disease if they were to become infected. However, these people have been isolated from their families and many will die without having the chance to physically be with their loved ones. Our physical health is also threatened, not only for those sickened or killed by SARS-CoV-19, but also for people with other, noncritical, medical conditions, who may not have access to hospitals or testing facilities.

Many methods have been employed to slow the spread of this virus. We have either mandated or strongly encouraged people to wear various types of facial coverings whose effectiveness is controversial among those in the scientific and medical community. We have practiced social distancing. In many areas, we have closed parks and other recreational venues, replaced face-to-face schooling with online classes, and closed places of worship. We did succeed in flattening the curve in many places for months, yet some parts of the developed world are now seeing the numbers of reported cases spiraling out of control as the number of new cases breaks records daily. Some of the increase in the number of people testing seropositive may be due to the massive testing efforts detecting more cases. Some of the increase may result from the reopening of businesses and other venues, which led to the exposure and spread of disease among those previously isolated from contact with infected people. Fortunately, the mortality rate is decreasing.

A second round of COVID-19-related shutdowns has been advocated in some areas, but as time goes by, thoughts about implementing this drastic action continue to change. The economic and societal impacts of both our inactions and actions will likely be felt for many years. If another round of shutdowns is mandated, this action may save lives or damage the world’s economic health even further or both. Shutdowns are particularly devastating to impoverished people in the developed world and, even more so, to those living in the developing world. As the numbers of COVID-19 cases and hospitalizations continue to increase in some parts of the world, our understanding of the disease and our responses to it must also change. However, the resulting uncertainty in what constitutes the best practice for different segments of the population has caused rifts among scientists, physicians, and public health workers, in addition to the general population. The world post-COVID-19 may in some respects not ever return to the world that we knew before the emergence of SARS-CoV-2. Our previous jobs and understanding of a work environment, manner and quality of education, societal and cultural norms, and personal liberties may be irreversibly altered.

These major changes in our lives and our world occurred rapidly from the time that the first cases of COVID-19 were reported in China in December 2019 to the time of this writing (late July 2020). The emergence, spread, and increased virulence of other neglected viruses and viral diseases have also occurred in the previous two to three decades, most notably the rapid emergence of Zika virus-induced microcephaly among newborns and infants and Guillain–Barré syndrome in some Zika virus-infected adults. While the recent, large, and deadly Ebola outbreak did not seriously threaten the lives of people living outside of certain parts of Africa, it was devastating to the populations of the affected regions. Just as importantly, that Ebola outbreak occurred in an area of Africa that had previously been almost totally Ebola virus-free. Other large disease outbreaks in the previous decades include SARS, caused by a coronavirus that emerged in China and Hong Kong. It was quickly spread by air travel of infected people to other areas of the world and led to a major outbreak in Canada. The H5N1 avian influenza outbreak in 1997 was predicted to kill up to 100 million people, but instead killed less than 600 people over the course of two decades. The general public responded to the projected death rate with great fear that fortunately was unwarranted. Some leaders of the public health community are currently warning of a potential pandemic of a novel strain of H1N1 influenza during the next “flu” season, in addition to a second wave of COVID-19. Public health recommendations and mandates may again be implemented that threaten to rip apart the fabric of human society even further.

Flaviviruses and Their Vectors

This book dealt with the potential threats of novel or neglected flaviviruses or flaviviruses that have the potential to emerge or reemerge as they adapt to better survive and replicate in human hosts. Natural or man-made changes to the environment and ecosystems further disrupt long-standing viral transmission cycles as the behavior and range of the viruses’ vector and reservoir species change. Since almost all flaviviruses are arboviruses, transmitted by mosquitoes and ticks, measures have been undertaken to decrease human exposure to the disease vectors, including extensive educational programs. The effectiveness of some of these measures is unknown. The vast campaign to contain West Nile virus in North America to New York City and the surrounding area appears to have been unsuccessful since the virus spread from coast to coast in the United States and southward and northward into Mexico and Canada in less than 5 years. We do not know, however, the extent to which this campaign mitigated the incidence of severe West Nile cases. Fortunately, while still a threat, the number of West Nile cases in much of North America peaked between 2003 and 2006. This is likely due to the decreased number of immunologically naïve human hosts resulting from herd immunity caused by large numbers of prior, asymptomatic cases.

Severe diseases caused by other flaviviruses, particularly dengue hemorrhagic fever and dengue shock syndrome, are continuing to spread as mosquitoes adapt to life in urban conditions ( Aedes aegypti ) and increase their range into more temperate zones ( Aedes albopictus ). Decreasing human exposure to mosquitoes and ticks should decrease disease incidence in humans. Large-scale, long-term elimination of these vector populations would, however, be extremely difficult. We have, however, had some significant successes in decreasing populations of disease-carrying mosquitoes. These successes include the dramatic reduction of yellow fever in Panama, which allowed the construction of the Panama Canal. Nevertheless, many areas that had substantially reduced mosquito populations are now seeing their return. Over a century ago, yellow fever was also virtually eliminated from the mainland of the United States, where it had previously occupied areas of the American South. These areas are still free of nontravel-related yellow fever.