Climate change and infectious disease: How sick will we get?

Rising seas and melting polar ice caps and glaciers documented by impressive satellite imagery capture the attention of the news media and make headlines.

Yet, the most consequential aspect of any change in climate, no matter the cause, receives scant attention. The single most pressing repercussion of any significant alteration in climate, whether global in scale or localized, will be in the shifting patterns and distribution of infectious diseases.

{mosads}Substantial alterations in either localized or global temperature and humidity can directly relate to the distribution and virulence of many microbial pathogens, no matter the underlying cause. This correlates with the rich complexity and diversity of all ecologies in which pathogens thrive. So shifts in the distribution of vegetation, the dispersal and range of animal predators or their prey, or distortions in the variety, concentration or specific strains of vectoring insects or disease carrying organisms can all influence the transmission of pathogens or their relative abundance.
We Can Already See Its Effects

It is believed that some changes in the patterns of infectious disease can be currently observed and are even now being experienced. For example, malaria spreading to the highlands in Africa and the northward spread of West Nile Virus in the United States has been linked to the changing distribution of disease carrying mosquitoes relating to climate change. So have shifts in the spread of dengue fever in endemic areas. Moreover, a wide range of diseases can be transmitted to humans from animals, such as Ebola, which is believed to originate from fruit bats. A shifting climate may enhance the likelihood of that cross transmission or the virulence of any viral or microbial strains that do so.
The Interactions Between Microbes, Man, Climate and Geography are Complex

Of course, ecological variation has been ever ongoing over earth’s history, and that of man’s time on earth also. We, as humans, have been both victims of pathogens and carriers too. For example, the loss of the North American large mammals, like the woolly mammoth and saber-toothed tiger, has been correlated by some researchers to a phenomenon termed hyper-disease. Man’s unparalleled capacity for far ranging travel may have made him or his traveling companions such as hunting dogs, the unwitting carriers of new and novel pathogens brought to the New World from the Old and contributing to or even causing an epidemic extinction of the indigenous large mammals in the Americas 12,000 years ago.
Today, we have an even greater capacity for world wide and nearly instantaneous travel. The globe is interconnected as never before. In any ecosystem, whether on land or in water, if the balance of immunological accommodation is upset, far-reaching health consequences can be anticipated. There may be unexpected outcroppings of old pathogens or susceptibility to new ones. Distinct or more virulent infectious diseases can emerge when immunological defenses are unprepared. Long quiescent plagues could resurface. So, a changing climate carries many contemporary and future risks.

The Stakes are Higher Than We Previously Thought.

Furthermore, new evidence informs us that there are previously little understood deep interconnections between microbial life and all larger creatures, even we humans. It is now understand that all complex organisms are vast collections of microbial and innate cells in linked cellular environments that have been previously appraised as one single organism. There is a prodigious and constant interchange among these microbial cells, which are coexistent within any organism, its own innate cells and an agitating external microbial realm. It is now believed that this interplay can have an evolutionary impact. So the possibility of even greater sequela than previously understood exists.
What Response Makes the Most Sense?

How then should this affect our global response to climate issues?

  • First, an increased awareness of the intricacy of the connections between climate change and infectious disease is necessary.
  • There should be redirection of some of the scant resources available for climate research or remediation towards accurately assessing how the patterns of infectious disease might vary and the potential ramifications of such changes. For example, expensive projects of carbon capture and sequestration are avidly discussed and have strong lobbies; but, there is absolutely no means of accurately predicting if they will be of any use or simply immense wasted expenditures.
  • Whether climate change is present now or only eventually, devoting resources and conducting research studying the patterns of communicable disease is our most appropriate response at this time. These initiatives would include evaluating and implementing better means of mosquito, tic and rat control, assessing patterns of carrier animal migration, sharpening our tracking of current patterns of communicable diseases, and aggressive research into improved therapies. All of these would yield substantial benefits with certainty.

Miller has been a physician in academic and private practice for over 30 years. He is the author of The Microcosm Within: Evolution and Extinction in the Hologenome. He currently serves as a scientific adviser to OmniBiome Therapeutics, a pioneering company in discovering and developing solutions to problems in human fertility and health through management of the human microbiome. For more information,


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