Amidst a global pandemic, one might find themselves with a lot more time to think than usual. Something everyone should begin to examine more is how they can make small, measurable changes to their lifestyle in order to help globally reduce the detrimental effects on our climate. Why, might you ask? Increasing evidence exhibits a strong connection between our changing climate and an increased frequency of disease. Understanding this process offers both illuminating and alarming information with only one conclusion—COVID-19 is only the beginning.
Climate change is a naturally occurring process and can most easily be described as an imbalance between incoming and outgoing atmospheric radiation (Shuman 1). Despite this, facts have long demonstrated humans are playing a key role in speeding up the detriments. The tangled web we are weaving is a clear consequence of global impact.
As displayed in the cascade below, multiple factors begin to trickle downward along the climate cycle. These include the thawing of the permafrost, increased precipitation, perpetuation of warmer temperatures, and mass movement of people and animals. Each of these major events has myriad effects on other aspects of life, most resulting in or having some effect on an increased emergence of disease (Figure 1).
One of the biggest questions arising from this global pandemic is where the virus might have originated. One must search quite far to discover the thread answering this question.
As global temperatures rise, the hydrologic cycle is predicted to change in response (Shuman 1). This might explain the higher than average rainfall in the United States this past spring. As you can see in the figure above, incubation time for insect larvae, particularly of the parasitic variety, shortens at higher temperatures. A warmer climate also increases the range and movement of parasitic hosts and has an effect on biting rates and persistence of biting (Short, Erica E et al. 4).
Insect vectors also tend to be more active at higher temperatures (Shuman 1). Data like this might explain the recently increased prominence of ticks. Surprisingly, tick populations have surged in subarctic areas in Russia and Canada, and especially in places with mild winters (Short, Erica E et al. 11). Other hosts for disease and virus include snails, arthropods, livestock, and even your resident dog or cat.
Raising of livestock often poses an issue by itself; a mass of animals existing in high density, all within the same age range, health condition, and genetic similarity (Engering et al. 5). This provides a sort of “bacteria buffet” for pathogens and viruses to thrive. An example of this viral effect on the general population would be a salmonella recall. As these animals are inoculated using the same vaccines, eventually some of those diseases might develop an antibiotic resistance, allowing them to spread quickly and infect many.
Now, viruses and protozoa can also exist in absence of a host environment, and some of these can be transmitted through contaminated drinking water. As the icecaps melt and the volume of liquid in our waterways increases, heavy rainfall events will become more regular. The contrast to this is as the climate warms, drought will also persist. This can in turn cause crop stresses; farmers will compensate with increase use of fertilizer and pesticide application (Engering, Anneke, et al. 15), which can then contaminate nearby water systems. Additionally, heavy rainfall events offer transportation for water-borne pathogens, such as giardiasis. Giardia intestinalis is a parasite ingested via contaminated water, in extreme cases causing diarhea, fatigue, and cramps. Increase in rainfall can drive biodiversity into diminished habitat areas, allowing for greater pathogen-host interplay. Ultimately, warming temperatures will play a great role by increasing the pathways viruses, diseases, and parasites can travel.
As people and animals are driven into close quarters, interaction between species increases significantly. According to the US Centers for Disease Control and Prevention (CDC), three quarters of new or emerging diseases that infect humans originate in animals. Our activity, such as our continued tendency to gravitate towards cities, multiplies the risk of contagion (Watts 1). The UN estimates that 55% of people worldwide live in cities, which has surpassed the 4 billion mark (Ritchie 1).
As these urban areas expand, fragmentation of livable habitat for animals occurs, causing species endangerment and quick transmission of disease. An example of this rapid transmission is evident with the spread of malaria. Malaria did not previously exist in the highland regions of East Africa; the warmer and saturated climate allowed the disease to spread and result in high rates of illness and death (Shuman 1). Trends like this will continue to emerge if rapid action is not taken.
Unfortunately, glaring disparities exist in the racial and socioeconomic classes affected by gross environmental oversight. As discussed, growth of cities and increased habitat destruction are an essential component for emerging diseases to generate. The World Health Organization has released data regarding the effect of climate change on human health and predicts that impacts will increase significantly in lower income, less developed areas (IPCC 1). This is directly imbalanced with areas of concentrated wealth, who often contribute considerably more to greenhouse gas emissions. The economic costs both in loss of life and quick spread of disease is yet another casualty of the warming climate.
In regard to the novel Coronavirus (SARS-CoV-2), you may now have gathered some new insight on the myriad factors that may have led to its proliferation. The genetics of the disease were traced back to a bat, but an (currently unknown) intermediary was necessary to pass the virus to humans (Watts 1). As we rush to generate a vaccine and establish a return to “normal life,” we neglect to consider a few important points.
The first and perhaps most glaring issue is all of the things previously listed that contributed to the emergence of COVID-19. Efforts to mitigate individual and global impacts on climate change need to be shifted to the forefront of our concerns. Secondly, the use of a partially effective (i.e. rushed) vaccines to control or mediate the effects of COVID-19 may drive the selection of a more antibiotic resistant and dangerous strain of the virus (Engering, Anneke, et al. 6). Despite momentous advances in medicine, scientists will have no idea what the long-term effects of this expedited vaccine will be.
Finally, it would be vastly more effective to focus our efforts on proactive risk management, rather than responding after a crisis (Hoberg and Brooks 5). We cannot stop emerging disease or climate change, but it would be much less expensive to both the population and the global wallet if a stand was taken against climate change now. I would imagine the millions affected by loss of loved ones to viruses like COVID-19, SARS, MERS, and Ebola would feel the same way.
WORDS: Elizabeth Kantra.
Engering, Anneke, et al. “Pathogen–Host–Environment Interplay and Disease Emergence.” Emerging Microbes & Infections, vol. 2, no. 1, 25 Jan. 2013, pp. 1–7., doi:10.1038/emi.2013.5.
Hoberg, Eric P., and Daniel R. Brooks. “Evolution in Action: Climate Change, Biodiversity Dynamics and Emerging Infectious Disease.” Philosophical Transactions of the Royal Society B: Biological Sciences, vol. 370, no. 1665, 2015, p. 20130553., doi:10.1098/rstb.2013.0553.
IPCC. “Climate Change and Human Health – Risks and Responses. Summary.” World Health Organization, World Health Organization, 25 Oct. 2012, http://www.who.int/globalchange/summary/en/index2.html.
Ritchie, Hannah. “Urbanization.” Ourworldindata.org, 2018, ourworldindata.org/urbanization.
Short, Erica E et al. “Climate Change Contribution to the Emergence or Re-Emergence of Parasitic Diseases.” Infectious diseases vol. 10 1178633617732296. 25 Sep. 2017, doi:10.1177/1178633617732296
Shuman, Emily K. “Global Climate Change and Infectious Diseases.” New England Journal of Medicine, vol. 362, no. 12, 2010, pp. 1061–1063., doi:10.1056/nejmp0912931.
Watts, Jonathan. “’Promiscuous Treatment of Nature’ Will Lead to More Pandemics – Scientists.” The Guardian, 7 May 2020, pp. 1–1.