By Daniela Cassano and Shawn D’Arezzo
As the coronavirus still manages to infect and kill millions around the world, scientists are not only scrambling to find a cure, but they are also attempting to determine how and why people are contracting the disease. The first case of this disease was reported on December 31, 2019, in Wuhan, China. Three months later, the entire world begins shutting itself down. Many people wonder how the disease spread this widely and quickly. Although researchers cannot point out the exact details of the origins of the virus, it is clear that the coronavirus has become another pandemic that was started by animals and animal markets.
It is widely known that most plagues and pandemics that have happened in the past can be classified as zoonotic diseases or a disease where germs are spread between animals and humans. Some of history’s deadliest pandemics could be classified as zoonotic diseases, such as the Bubonic Plague, the Swine Flu, and the Zika Virus. With the emerging information that the coronavirus origins originated from animal consumption in Wuhan, China, it is impossible to ignore the comparisons to past zoonotic diseases. In this article, we are going to explore and explain the importance of knowing how diseases can spread from animals to humans.
Animals and Covid-19
The novel coronavirus’s origins in Wuhan, China are mostly categorized only by the fact that it came from wet markets in the city. Dr. Hansa D. Bhargava explained in her WebMD article Coronavirus History that these markets are “where customers buy fresh meat and fish, including animals that are killed on the spot.” When there are a high volume of people and/or products at such markets it “let[s] viruses from different animals swap genes”, which can lead to so many mutations that it can affect humans (Bhargava, 2020). Major outbreaks, such as the Covid-10 pandemic, have been the result of humans interacting with animals carrying zoonotic disease. Most human interference, according to a journal entry titled “The Origin and Prevention of Pandemics” from the work Clinical Infectious Diseases, comes from “the hunting and butchering of wild nonhuman primates” and, in other instances “keeping primate pets” (Hughes et. all, 2010). The hunting and the butchering of some of these animals and then later on selling them in crowded markets can lead to a widespread potential disease after consumption.
With the various amount of game that the Wuhan, China market had to offer during the beginning of the outbreak, it could be difficult to pinpoint the exact zoonotic host that caused the initial outbreak. Early hypotheses suggest that bats were the main zoonotic host, but it was debunked because bats were not on the market during that time. A study done by Xiaoqiang Huang, Chengxin Zhang, Robin Pearce, Gilbert. S Omenn, and Yang Zhang used Spike receptors to represent the coronavirus and ACE2 receptors to represent multiple hosts in order to determine which animal is the main host of Covid-19. In their findings, they concluded that some of the highest binding rates occurred with the marmoset, the Malayan pangolin, and turtles. The different groups all achieved high standards based on the different tests that were calculated such as their binding energy rates, its shared identities with other receptors, and how much these animals would interact with humans in a market situation. However, the results of the experiment are not concrete, but only mere predictions. Because of this, the authors of this study conclude that the main zoonotic host remains elusive for now (Xiaoqiang et. all, 2020). As more information arises, the main host could be classified, but for now, it is safe to conclude that the start of the actual Covid-19 pandemic is a result of the wet markets at Wuhan, China, and the human consumption of game from those markets.
Role of Animals in Past Pandemics
One example of animals being a major influence in the spreading of disease is probably the most well-known example: the Bubonic Plague. Around the mid-1300s, the Bubonic Plague, also known as the Black Death, started becoming a major health issue across Europe, Asia, and Africa and lasted for centuries. In London, England, the plague became the leading cause of death in 1665 with a death total of 68,596 (Bills of Mortality, 1665). The infected person would experience many symptoms, including delirium, intolerance to light, fever, fatigue, and more. Eventually, many parts of the body would swell up, specifically the victim’s groin and armpits. They would then die quickly from a mixture of vomiting, bleeding, and the death of skin cells (Kew, 2019).
In the article “Black Death Bodies” by Sharon N. DeWitte, DeWitte states that plague is spread when an animal or person is bitten by a flea containing the Y. pestis bacteria. From there, the disease can be spread through the air (DeWitte, 2017). With fleas transferring blood between most animals that they encounter, it is no wonder that the majority of living beings across Europe ended up carrying the deadly disease.
During this time, it was very common to come across fleas because of the lack of public sanitation. You could find them in the street, in every house, and in every public building. Therefore, it is understandable that many people would get bitten by an infected flea or an animal previously infected. When a human would get bitten by an animal that was carrying the plague in its bloodstream, the disease would be transferred through the rat’s saliva. Then, the saliva would sink into the person’s body, infecting them.
From there, it was not only very easy for the disease to spread between humans, but there were also numerous ways that it could spread from person to person. The most common method of catching the disease was breathing in the air in which is released from the patient since the air would contain respiratory droplets that would contain the bacterium. The combination of contracting the disease through direct contact, the breath of the infected, and the bite of one of the most common animals seen around humans at the time made the Bubonic Plague one of the easiest diseases to contract.
The second disease that is known for being a zoonotic disease is the Flu. Swine Flu is a mutation of the influenza virus that was found in pigs around 2009. This is a disease that was relatively new in 2009 so when many people around the world started to develop symptoms of the disease, no one knew how to stop it or know how it was caught. As reported by Centers for Disease Control and Prevention (CDC), “From April 12, 2009, to April 10, 2010, CDC estimated there were 60.8 million cases (range: 43.3-89.3 million), 274,304 hospitalizations (range: 195,086-402,719), and 12,469 deaths (range: 8868-18,306) in the United States due to the (H1N1)pdm09 virus” (CDC, 2019).
This disease was transferred from pigs to humans in the simplest way possible. The disease was spread from touching infected pigs or from breathing in the air exhaled by an infected pig. Then, the disease could be spread from person to person in the same two ways. While it seems like common sense since it is a mutation of the influenza virus that was seen during the Influenza outbreak in 1918, Swine Flu still infected millions across the United States in 2009.
Why This Knowledge Is Important and Concluding Information
The trend between humans and the spread of zoonotic disease should not be ignored. Especially with the Covid-19 pandemic at large, recognizing that humans are also mainly responsible for the spread of some of the world’s deadliest pandemics is necessary. The wet market that started the novel coronavirus in Wuhan, China carried the zoonotic host that was eaten by one person, and it spread throughout the entire world. Numerous pathogens can be caused by hunting, the trading of animal foods, and even by keeping exotic animals as pets. If one of these practices is not handled appropriately, there is bound to be some sort of contamination through a cross-species transmission that can greatly harm another human being. As historically demonstrated in the past, the more interaction an infected person has with other people, the greater of a chance there is of a potential outbreak. So we cannot blame severe outbreaks on the animals themselves when there is a larger component with human activity and interaction.
It is incredibly important to find out how Covid travels between each species because that knowledge could help speed up the process of finding a vaccine for the disease. For example, in 1665, the Bubonic Plague was the leading cause of death in Europe. People did not know that the disease originated from rats and the fleas that spread the plague bacteria. Since they did not have that knowledge, the people could not find a cure and had to wait out the disease until it subsided. This left about a quarter of London’s population to die because of the disease.
The difference in these two situations is the knowledge of each situation. When a group of people knows of a disease, it is much easier to find ways to prevent the disease from spreading. This provides the population more time to find either a cure or more ways to help mitigate the spread and effects of the disease. This is why we, as a global population, should work together to research the various ways that Covid can spread between all species. While it is impossible to research every single species across the world, we should focus on seeing if and how the disease is transmitted between people and common found animals. Once we have this knowledge, we are one step closer to finding a cure that can end the global pandemic.
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References
Bhargava, H. D. 2020. Coronavirus History. Retrieved from https://www.webmd.com/lung/coronavirus-history#:~:text=Experts%20say%20SARS%2DCoV,%E2%80%9Cwet%20markets.%E2%80%9D
Center for Disease Control and Prevention. 2019. 2009 H1N1 Pandemic (H1N1pdm09 virus). Retrieved from https://www.cdc.gov/flu/pandemic-resources/2009-h1n1-pandemic.html#:~:text=From%20April%2012%2C%202009%20to,the%20(H1N1)pdm09%20virus
Damen, M. 2019. Man and Disease: The Black Death. Retrieved from http://www.usu.edu/markdamen/1320hist&civ/chapters/06plague.htm
DeWitte, S. N. 2017. Black Death Bodies. Retrieved from https://lms.hypothes.is/lti_launches?url=https%3A%2F%2Fquod.lib.umich.edu%2Ff%2Ffrag%2F9772151.0006.001%2F–black-death-bodies%3Frgn%3Dmain%3Bview%3Dfulltext
Huang, X., Zhang, C., Pearce, R., Gilbert, O. S., Zhang, Y. 2020. Identifying the Zoonotic Origin of Sars-CoV-2 by Modeling the Binding Affinity between the Spike Receptor-Binding Domain and Host Ace 2. Retrieved from https://zhanglab.ccmb.med.umich.edu/COVID-19/paper3.pdf
Hughes, J. M., Wilson, M. E., Pike, B. L., Saylors, K. E., Fair, J. N., LeBreton, M., Tamoufe, U., Djoko, C. F., Rimoin, A. W., Wolfe, N. D. 2010. The Origin and Prevention of Pandemics. Retrieved from https://academic.oup.com/cid/article/50/12/1636/305066
Kew, R. 2019. Great Plague of 1665-1666: How Did London Respond To It? Retrieved from
