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Calling SARS-CoV-2 “the coronavirus” has created a lot of confusion. “Wait, my cat had coronavirus last year, what was that?” Or “My son was sick with a cold at last year and my doctors said it might be coronavirus. Was there coronavirus last year?”
SARS-CoV-2 is a “novel” coronavirus. “Novel” means “new” or at least “newly discovered.” But there are other species of coronavirus that have been affecting a variety of animals, including humans, before SARS-CoV-2. The ones most people are familiar with are feline coronavirus in cats and the common cold in humans.
Feline Coronaviruses and FIP
Feline coronavirus (FCoV) was discovered in 1963. It is frequently transmitted between domestic cats that share a home or live in a shelter together. The common strains that are less harmful and typically associated with the GI tract are referred to as Feline enteric coronavirus (FECV). FECV is often asymptomatic, meaning the cat has no symptoms at all. This allows it to spread, as people don’t know their cats are infected and allow them to interact with other cats and share litterboxes. FECV can cause mild diarrhea and/or respiratory symptoms in some instances, but cats’ immune systems generally clear the virus and they go on to live a healthy life.
Some cats don’t get better because they have a more virulent (higher mortality) strain of FCoV. The virus develops a mutation that allows it to effectively move out of the GI system and cause feline infectious peritonitis (FIP). In these cases, the virus infects white blood cells, spreads to various organs, and causes a massive inflammatory response that is usually fatal. There are no approved treatments for FIP in the US, but there is an experimental treatment which may be available.
The less the virus is allowed to circulate among housecats, the fewer opportunities there are for it to mutate. A concern is that a mutated version of the virus could become widespread, leading to increased death of housecats. So far, however, this has not occurred.
Canine Coronavirus
There is also a canine coronavirus (CCoV) which was discovered in 1971 and follows a similar pathobiology to FCoV. Both the feline and this canine coronaviruses are from the group of coronaviruses with which we are most familiar. There is another coronavirus from a smaller sub-genus that affects dogs, called canine respiratory coronavirus.
Humans: The “Common Cold”
Several human coronaviruses cause the human cold. In total, more than 200 different species of virus from the coronavirus and other families are known to be causes of the common cold. Nevertheless, about 20% of colds are caused by viruses that circulate in the population but have not yet been identified. About 20% of colds are caused by coronaviruses, and almost everyone has at least one coronavirus cold over the course of their life.
Most people are a little uncomfortable from a cold, but that’s it. However, some people, such as those who are immunosuppressed or have lung, heart, or certain other pre-existing conditions can die from the common cold. Certain primates can catch a variety of common cold viruses from people that are much more fatal in non-human primates. The immune systems of non-human primates do not have the ability to fight off infection, similar to what is happening with people and SARS-CoV-2.
Because of the relative lack of risk of the common cold in humans, research on treatments has included other goals such as decreased economic burden on people who get the cold. Those who are now called “essential workers” are often most impacted economically by the common cold. They usually work in high-traffic settings where they have the most risk of getting a cold, and they often have little room in their budgets to be home sick or to be caring for a child who is home sick. Better prevention and treatment of the common cold could reduce the economic burden on the most economically vulnerable.
In recent years, more dangerous coronaviruses have come on the scene, including the viruses that cause SARS, MERS, and COVID-19. Smaller outbreaks of serious coronaviruses have received less attention or may even have been undetected.
Coronaviruses in Other Animals
Pigs, ferrets, mink, mice, chickens and turkeys all have diseases specific to them caused by coronaviruses. As we all know by now, so do bats. There is even a coronavirus specific to Beluga whales.
Each of the coronaviruses has evolved to be specific to a cell receptor of a specific species. Without matching that receptor, the virus cannot get into the cell and replicate. While some coronaviruses can attach to cells in multiple species of animals, most cannot.
SARS-CoV-2, the coronavirus that causes COVID-19, is most able to infect humans. It likely evolved in bats and then spread through an amplifier species to humans. It has rarely been able to infect dogs, cats, and minks. In contrast, common cat and dog coronaviruses have never been known to infect a human, and the human coronaviruses that cause the common cold have never been known to infect animals other than non-human primates.
Conclusion
Coronaviruses that we already have experience with in pets, livestock and people mirror some of the concerns that have come up with the novel coronavirus, SARS-CoV-2. These concerns include asymptomatic transmission and risk of mutation when circulation of the virus is high. This risk of mutation includes the development of a virus that affects a different species than the original host.
The fact that coronaviruses can evolve to infect other species makes them a “zoonotic” disease, that is, a disease that can be passed from animals to people. “One health” is a concept that looks at how the health of humans, animals and the environment interact. This approach is required to keep both humans and animals safe from coronaviruses. We need to avoid situations where we can pass coronaviruses to other animals to protect them. Reducing coronavirus infections in pets and livestock reduces the chances that their coronaviruses will mutate to be able to impact other animals, including us. Avoiding contact between wildlife and humans, pets and livestock prevent wildlife coronaviruses from making the jump closer to humans.
References
DerSarkissian, C. (Reviewer). (2019). What’s causing my cold? Available at: https://www.webmd.com/cold-and-flu/cold-guide/common_cold_causes
Baldassarre, M. E. et al. (2020). Resveratrol plus carboxymethyl-β-glucan in infants with common cold: A randomized double-blind trial. Heliyon, 6(4), e03814. doi:10.1016/j.heliyon.2020.e03814 https://pubmed.ncbi.nlm.nih.gov/32322697/
Le Poder, S. (2011). Feline and canine coronaviruses: Common genetic and pathobiological features. Advances in Virology, 2011, 609465. doi:10.1155/2011/609465 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3265309/
Cornell Feline Health Center. (2020). Feline infectious peritonitis: What is FIP? Available at: https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information/feline-health-topics/feline-infectious-peritonitis