It’s Earth Day. It’s Also Time to Talk About Climate Change’s Role in Causing Pandemics.

Vaccinating the World
By Katie Foley

The emergence of COVID-19 in Wuhan, China and its rapid development into a global crisis has augmented existing research about disease outbreaks and their spread. For some time, public health and climate science researchers have been asking: how do we prevent diseases jumping from animals to humans? And, in an increasingly interconnected world, how do we mitigate disease spread among humans? A large body of research is dedicated to the detection of new diseases in animals and the prevention of zoonotic transmission (between animals and humans). According to the CDC, approximately 75% of emerging diseases that infect humans originate in animals. This risk to humans is twofold: interaction with wild animals and with farmed animals. For example, human disruption of natural habitats through industry–such as logging, mining, and road building–increases the likelihood that humans will come into contact with unfamiliar wild animal species and unfamiliar diseases.

In the case of COVID-19, humans came into contact with wild animal vectors at an informal market that slaughtered animals–including chickens, donkeys, sheep, pigs, foxes, and various reptiles–right in front of customers. In early March, China acknowledged the connection between this practice and the current public health crisis and introduced a ban on consumption and farming of wild animals. Nevertheless, it may be difficult to curb the trade of wild animals in China, where they are used as food, traditional medicine, clothing, etc. Informal markets like the one in Wuhan are often culturally and/or nutritionally important, especially in parts of the world without access to refrigeration, but they do increase the risk of new diseases moving from animals to humans.

Additionally, factory farming practices around the globe contribute to disease spread, both among farmed animals and between these animals and humans. According to Dr. Dennis Carroll, Director of USAID’s Emerging Threats Unit, “As the human population grows, we see an increased appetite for animal protein. And in response we are raising livestock at unprecedented levels. The problem with that is that the sheer number of animals in a confined space elevates the risk for a virus to spread and mutate at a rapid pace.” The documentary Dominion details the abusive and unsanitary conditions animals endure in the factory farming industry. Egg-laying hens undergo intense physical stress to lay 20-30 times the amount of eggs they would in the wild; turkeys often live in their own waste; and ducks, without water for swimming, often fail to keep their eyes, nostrils, and feathers clean. These conditions take a toll on the health of these animals, increasing their vulnerability to contracting and spreading disease.

As the COVID-19 pandemic intensifies, the animal agriculture industry–an industry where workers “typically stand elbow-to-elbow to do the low-wage work of cutting, deboning, and packing” meat–plays a large role in perpetuating the coronavirus’ spread. Right now, animal agriculture companies should adjust to up hygiene and social distancing measures, as well as encourage employees to stay home if they’re feeling sick. On the contrary, major companies in the animal agriculture industry have executed slow responses and many are offering financial incentives to workers who show up: at a Tyson plant in Camilla, Georgia, the company offered its 2,100 workers a $500 bonus if they worked April through June without missing a day. For low-income and immigrant workers (and particularly undocumented workers), these financial incentives, coupled with a lack of paid sick leave, are extremely effective at keeping workers in the plants regardless of how fearful and/or sick they may feel, accelerating the spread of COVID-19 in their communities.

Many researchers point to climate change as a variable that can increase the speed at which diseases are transmitted and which geographic areas are most vulnerable. All diseases and their vectors have ideal environments, affected by precipitation, temperature, etc. for growth, survival, transport, and dissemination. As climate change escalates average temperatures and exacerbates extreme weather events, certain diseases may spread to new populations and/or develop on different timelines. In the cases of dengue and malaria, warmer temperatures speed the development and feeding timeline of mosquitoes, in turn speeding the development of the malarial parasite within the mosquitoes, and resulting in mosquitoes biting humans sooner. In other words, any virus carried by mosquitoes spreads faster in warmer climates.

Alternatively, the effects of climate change on the potential for influenza transmission is unclear. While seasonal influenza tends to peak in winter months, researchers largely suggest that this trend is due to increased indoor crowding both at the beginning of the school year and during the winter rather than temperature-dependent disease transmission. Similarly, experts reject President Trump’s assertion that the onset of warmer weather will slow the spread of COVID-19 because its spread has persisted in more temperate climates already. If anything, climate change may alter the way we experience flu season. According to Scientific American, “In the warmer tropics … flu season tends to spread out throughout the year, with some spikes during the rainy season. As a result, some experts suggest that climate change may cause flu outbreaks in temperate regions to become less intense but more evenly distributed across the seasons.”

On the whole, the COVID-19 pandemic generates food for thought: we are currently living through one of the impacts of human-driven climate change (in addition to the rising sea levels, depletion of polar ice, extinction and migration of various species, and “once in a lifetime” natural disasters that come every few years now). How can we persuade policymakers to respect the natural habitats of wild animals? How can we urge the animal agriculture industry to prioritize the health and well-being of both its workers and farmed animals? And, what steps can we–and should we–be taking now to mitigate climate change and prevent future public health crises?

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