If you’re not a member of the scientific or medical community (or, if you are, you're a hero right now!), it might seem like the novel coronavirus came out of nowhere. Now that 191,127 COVID-19 cases in total have been reported on every continent except for Antarctica, many people are wondering exactly where the novel coronavirus came from.
While a lot about the virus is still unknown, part of the answer to that mystery may have to do with an animal more commonly thought of as an important part of any good Halloween decoration display: the bat.
The first cases of COVID-19 (the illness caused by novel coronavirus) can be traced back to a live animal market in Wuhan City, China, according to the CDC. And research suggests that, like other recent viral outbreaks, COVID-19 originated in bats before it made the jump to humans. Here, the details on how bats played a role in this COVID-19 outbreak.
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How did bats get the novel coronavirus in the first place?
It's unclear exactly how bats picked up novel coronavirus, but researchers do know they carry it and are the reason it's been passed on to humans. COVID-19 is a zoonotic disease, which means it is caused by an animal virus that has been picked up by humans, explains Richard J. Kuhn, PhD, a professor of biological sciences at Purdue University. By Kuhn’s estimate, about 80 percent of viruses that exist are zoonotic viruses, and they work in both directions: animals can pass them to humans, and humans can pass them back to animals.
The novel coronavirus that caused this current outbreak comes from a family of zoonotic viruses. Viruses from this family have been passed to humans from animals before (more on this later) and usually result in cold- and flu-like respiratory symptoms for humans. But the illnesses they cause can also lead to death in animals, according to a study from the University of California, Berkeley.
However, researchers have found that when bats contract these viruses, their particularly strong immune systems prevent them from getting sick or dying from the infections. This means they can continue to carry and pass on the virus, whereas other animals that contract it may get sick and die, and therefore are less likely to pass it on. The UC Berkeley researchers found that a bat’s immune system is so strong, in fact, that when a virus infects a bat, the animal’s immune system response is thought to cause the virus to adapt and replicate even faster. That means when the virus infects an animal with a weaker immune system (let’s say a human), the virus is able to wreak havoc.
One of the reasons bats have such strong immune systems is thought to be the fact that they can fly, according to the UC Berkeley study. When they fly, bats elevate their metabolic rates to a level that would hurt other mammals, but for bats, helped them develop an immune system that is able to quickly repair the cell damage caused by flight, the researchers found.
How did novel coronavirus spread from bats to humans, then?
As a virus jumps from species to species, it mutates, which means that researchers won't see an *exact* copy in animals of the novel coronavirus found in humans. But scientists have found a 96 percent genetic match between the virus that's currently infecting humans and a coronavirus that is found in bats, according to a study published in Nature in February.
Kuhn believes that it’s not likely that novel coronavirus spread directly from bats to humans, but that one or more animals at the market in Wuhan were infected by bats and served as an intermediate host in the transfer of the virus from bats to humans. It's thought that humans then came in contact with an infected animal, or animals, at the market. How exactly the virus was transmitted is still unknown, but some theories include a human consuming an infected animal or touching an infected animal during the butchering process.
While they don't know the exact route the virus took to get to humans, scientists all seem to agree that the novel coronavirus came from animals—particularly considering other recent disease outbreaks that were caused by zoonotic viruses.
What other illnesses have been linked back to bats?
COVID-19 is not the first illness that has made the leap from bats to humans. The viruses that caused SARS, MERS, Ebola, Nipah, Hendra, and Marburg can all be traced back to bats, according to the UC Berkeley researchers, although all were spread through intermediate hosts. While animals and humans have traded diseases back and forth historically, recently, outbreaks that can be traced back to animals have become more common—partly, at least, due to human behavior.
"This is something that has been increasing probably because we’ve degraded their habitat and come in more contact directly with more animals," says Kuhn. He also notes that humans have created environments where there are high densities of animals, "whether that’s a swine farm or a wet market, in which viruses can spread," he explains. "So, there will continue to be this threat of pathogens moving into a new ecological niche."
Is there any way for people to prevent the spread of viruses from bats to humans?
Unfortunately, experts say no. Humans come in contact with animals in all sorts of ways—by hanging out with pets, consuming animal products, and encroaching upon their habitats. So, Kuhn says, the best thing to do is try to learn from this outbreak and try to be prepared for when the next one occurs.
“The question is, will we be able to predict this in the future?" he says. "And we’re not there yet. We can anticipate that it’s coming because of our more frequent exposure to animals, but we can’t anticipate what it’s going to look like right now.” For Kuhn, one of the keys is developing better technologies that can tell if someone is infected with a virus before they become symptomatic. That way, someone who is sick can be treated and take appropriate action sooner and will hopefully limit the number of other people infected.
So, while researchers continue to investigate these diseases, the most important thing you can do right now is make sure you keep yourself and those around you healthy, per the CDC’s guidelines, and look out for the symptoms of the illness in yourself and others, and seek medical help and testing if you suspect you or a loved one has it.
The novel coronavirus is especially serious for the elderly, those who are immunocompromised, and people with chronic conditions. The best way you can prevent the spread of the virus is to practice social distancing, wash your hands frequently, avoid touching your face, and implement these other hygiene habits that can help protect the health of your family and community.
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