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Can humans become hosts and infect animals with COVID-19? To answer that question, you need to understand where the novel coronavirus came from.
Words by Nimisha Agarwal
The onset of COVID-19 and the sheer scale of infections worldwide have led the world to question the origins of this deadly pandemic. The novel coronavirus is not the first disease to emerge from an animal species. In recent years, as our relationship with animals has gotten increasingly intense, so too has the prevalence of highly infectious zoonotic diseases.
But the question remains: how far can this pandemic go? Can humans become hosts and infect animals with COVID-19? And why is it important to understand the origins of coronavirus and reevaluate our relationship with other species?
Studies show that the novel coronavirus jumped from animals to humans, although we do not know which animal, specifically. Scientists used genome sequencing to arrive at this fact, studying the virus’s DNA to understand the disease and its origins. The data shows that the virus first jumped from animals to humans and that subsequent transmissions have been from humans to other humans. In some cases, coronavirus passed from humans to animals. While we are still unsure of how COVID-19 originates, scientists believe it could have developed through either of these two routes:
Coronaviruses, in general, have historically had a zoonotic origin. The Middle Eastern Respiratory Syndrome (MERS) and the Severe Acute Respiratory Syndrome (SARS) originated from camels and civet cats, respectively. Studies have also shown that bats are reservoirs of many coronaviruses. Bats, who can harbor multiple strains of coronavirus, often carry these viruses to other mammals. Since one in five mammal species are bats, the variety and spread of these viruses are vast, making it even more complicated to study the exact origins of viruses like COVID-19. However, studies have been able to narrow down the focus to a few major animal groups.
Research obtained from genome sequencing has shown that COVID-19 is 96 percent identical to a bat coronavirus. Scientists believe that the novel coronavirus could have been transmitted to humans when the receptor-binding domain (RBD) in the “spike” protein of bats latch itself onto ACE2 protein receptors in humans. However, studies show that the RBDs present differently in humans and bats, so the theory is still speculative.
From a disease transmission point of view, the Malayan pangolins may be a better explanation of the origin of COVID-19. The coronavirus found in pangolins is better optimized for attaching itself to human-like ACE2 proteins than the virus found in bats.
While the research is still inconclusive, COVID-19 did originate from an animal at some point, and the most plausible explanation is that COVID-19 had two or more animal hosts. Some research has shown that pangolins, who are widely trafficked illegally and killed for their meat and scales, may have facilitated the transmission of the novel coronavirus from bats to humans.
Research conducted by the University of California, Davis, has shown that a variety of animal species–from chimpanzees to bottlenose dolphins–can be infected with COVID-19. Other animals who can be infected include sheep, Chinese hamsters, deers, giant anteater, Siberian tiger, cows, cats, pigs, and horses.
Other research studies have also indicated that cats, dogs, ferrets, fruit bats, hamsters, and tree shrews can catch the virus. Animals have contracted infections at various zoos across the world. Lions and tigers in Bronx Zoo in New York, a tiger at a zoo in Tennessee, snow leopards at a Louisville zoo, and gorillas at a zoo in California all tested positive for COVID-19. A cougar also contracted COVID-19 at a wild animal exhibitor in Texas.
Several countries have also reported minks infected at various mink farms. In many cases, the virus spilled over from infected humans to animals and occurred at places where humans regularly interacted with animals in confined spaces.
Currently, there is no evidence that pets can carry COVID-19 on their skin or fur. However, some pets have contracted COVID-19 from their infected human companions. Two cats in New York were infected with the virus and showed mild symptoms. Two dogs in Hong Kong also tested positive for COVID-19. Research has indicated that cats are highly susceptible to getting infected with COVID-19. However, the overall risk of your companion animal contracting COVID-19 is low. The U.S. Food and Drug Administration recommends maintaining healthy hygiene for pets to avoid the virus, including keeping their skin and fur clean.
On mink farms, particularly in Poland and Denmark, mink caught the COVID-19 virus from infected workers. The virus mutated in mink, creating a variant that spread to humans more rapidly than the original strain. As a result, the Danish government announced the “culling” or killing of thousands of minks. Factory farms have become hotspots for infectious disease, but this is the first known human-to-animal-to-human transmission. Researchers identified the new strain as “Cluster 5.”
It is still important to note the novel coronavirus is not the only coronavirus. Many other coronaviruses are present in animal species and only mutate by natural selection. This process takes a long time, though increased human contact with other species through factory farming and animal agriculture may speed up the process. Several zoonotic pandemics have originated and spread from factory farms.
Though some pets like dogs and cats have reportedly tested positive for COVID-19, the number of pets tested and diagnosed for COVID-19 remains low. However, tests do exist, and labs have developed a COVID-19 test for pets. Pets should only go to a veterinarian facility if they show symptoms of COVID-19, which include fever, coughing, difficulty breathing or shortness of breath, lethargy (unusual laziness or sluggish), sneezing, runny nose, eye discharge, vomiting, and diarrhea.
As of February 20121, the number of new cases in the U.S. is going down. This decline is due to the rapid acceleration of vaccination in many states and increased social distancing. Workers in the meatpacking industries are still one of the most vulnerable groups to COVID-19. The fast-paced nature of their makes physical distancing is nearly impossible. These frontline workers and deemed essential by their companies, and many cannot take the necessary time off when they are sick. Instead, they are forced to come to work and put others at risk.
In many cases, the effectiveness of COVID-19 vaccines hinges on animal testing. Significant research has shown that testing drugs on animals does not mean that they will work on humans.
The furthering of the haves and have-nots during COVID-19 has led to the increased consumption of animal products. By understanding the origins of deadly zoonotic viruses, perhaps we can foster a more equitable existence for all sentient beings.
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