Zika is all over the news—and it is surely dangerous. However, the virus has limitations (for example, the limited geography of its vector mosquitoes in the U.S.) so it is likely to be well contained. The greater significance of Zika extends beyond its current spread. This is because it exemplifies the important emerging trend of a novel infectious agent that has swiftly become a global threat.
Why is this happening now?
Our modern circumstances are distinctly unlike any previous era. Humans now have the unique ability to travel quickly and widely. And, we often choose to journey with our favorite pets and plants. This unprecedented degree of mobility extends across every habitat on the globe.
Further, this global mobility now occurs during a phase of a rapidly shifting climate. Certainly, species migration and global climate change are not new, but it is only in this present moment that these factors are amplified via global travel in such a singular manner.
The results of this unusual conjunction are already apparent. For example, Zika’s advance across Europe and to the Americas has been extremely rapid. This is such an extraordinary event that at the beginning of this year, the World Health Organization declared Zika a global emergency in recognition of its rapid spread from continent to continent. Its rising incidence mirrors our prior concerns about the global scope of other recent epidemics such as Ebola or SARS.
Emerging infectious diseases
The World Health Organization notes that infectious diseases are emerging at a greater pace and spreading faster than ever before. There are at least 40 new infectious diseases that have emerged that were unknown only a generation or two ago.
For example, Zika was first identified in the 1950s and was initially confined to a narrow band of equatorial Africa and Asia. Monkeys were its primary host. Abruptly, it appeared in humans in Polynesia in 2013. Thereafter, it is suspected to have arrived in the Americas by plane, appearing in Brazil in that same year. Now it demonstrates pandemic spread throughout the Americas and the Caribbean. It is a flexible virus, too. It can be transmitted by mosquito bites, from mother to child, by sexual contact, or blood transfusions.
Chikungunya virus is also a newly emerging threat. Chikungunya is characterized by the sudden onset of fever accompanied by joint pains. It has a low mortality but is associated with a high frequency of chronic medical disabilities—some of which can be devastating. First identified in 1952 and initially confined to small outbreaks in West Africa, it has spread worldwide with millions of cases across Africa, India, and Asia. Only recently, it has appeared in the Caribbean and South America, and recently, there have been hundreds of cases in the U.S.
New threats from old diseases
Each of these is an example of a new enemy. However, there are also consequential old players whose distribution can also be affected by climate and global travel. For example, dengue fever is a mosquito-borne virus first described in China in about 200 A.D. For centuries, there were only sporadic epidemics. Yet, it surged dramatically after World War II. It is now a major factor in childhood mortality in the Pacific and the Americas. Only recently, it achieved a toehold in the U.S. Worldwide, it affects tens of millions on an annual basis. Even malaria, an old and persistent scourge, is demonstrating an increasing speed of transmission attributed to socioeconomic factors that include land use, population growth and urbanization, migration changes, and travel.
The role of travel in spreading disease
The spread of disease through travel is not itself new. For example, in the Middle Ages, bubonic plague originated in China and arrived by trading ships to Europe. That briskly led to a series of devastating epidemics in the 14th Century that is estimated to have killed one-third of the European population.
Yet, even these horrific results are not the limit of epidemic disease. Twelve thousand years ago, there were abundant giant mammals on the North American continent such as mammoths, saber-tooth tigers, and giant sloths. Suddenly, they all disappeared. The exact cause is not known. However, ‘hyper-disease’ is one prominent theory.
It is believed by some scientists that migrating humans or their companion animals inadvertently spread novel diseases from Asia when they crossed to the Americas and the indigenous megafauna had no natural immunity. In fact, extinction on the basis of infectious epidemics may not be rare. For example, the world’s amphibians are threatened by Chytrid fungus and the extinction of several amphibian species has been attributed to this pathogen.
What is the appropriate response?
If this is our current reality, what is the appropriate response? Expensive carbon projects are proposed by many climate enthusiasts. Those disputed schemes should be put aside. Instead, our scant resources should be directed towards relatively inexpensive ends with large rewards. The best means would be to concentrate on the remediation of infectious disease. This can be accomplished by mosquito nets, removal of standing water sources in endemic regions, research into improved treatments and vaccines, and a deeper understanding of the reproductive cycle of vector insects or other intermediary hosts.
Clearly, our concerns about climate should emphasize coping with and conquering infectious disease as the truest common denominator of human health and welfare and proper planetary stewardship.