COVID-19, and How Bats Could Help Humans
Lockdowns. Closures. Social distancing. Since you are reading this, I feel comfortable assuming you are human, like me. I will further surmise that you have at least heard of the new coronavirus, COVID-19, that is sweeping through communities around the world. The first few sentences of this post are comprised of phrases that have likely become far too familiar to you recently. We are living amid a pandemic – a time unlike any in our lifetimes. People are fearful, news reports are grim, and, if we are not careful, we may believe all hope is lost. Here is the thing, though: all hope is never lost.
Why, you ask? Because the threat of this virus has led scientists across the globe to unite for a common cause. Not just medical researchers, either, but those who study a wide range of subjects, including the topic of this post – bats. I imagine you are thinking: “Umm, I decided to read this because I wanted to know more about COVID-19… why are you changing the subject?” I am not, though! See, bats experience several viruses that are a threat to humans (like coronaviruses, ebolavirus, and herpesviruses), but, when bats contract those viruses, they often remain healthy. Understanding what biological mechanisms keep bats from getting sick could help us find ways to better protect humans.
The Good and Bad about Bats and Viruses
Based on the previous section, you may be wondering why bats have been discussed negatively in association with COVID-19. Unfortunately for us, since bats who contract viruses often stay healthy, they become viral reservoirs. This means the viruses continue to live, reproduce, and be transmitted between bats, and, occasionally, to humans. Members of the Scripps Research Institute published an article on March 17th confirming a natural origin of COVID-19, and discuss how bats are a likely source. I understand you may be inclined to feel harshly toward bats, but you know as well as I do that the bats did not band together to commission a viral onslaught against humans. They just have unique adaptations that allow them to cope with infections.
Thankfully, however, bat resistance to infection is not all bad. It provides a unique opportunity to study effective responses to human-threatening viral infections. Researchers have been studying bat immune responses to viruses for years, and are continuously learning more about what keeps them healthy under viral attack. One big difference in bat vs. human infection responses is related to inflammation. In humans, several viruses result in extreme inflammation, but bats have limited inflammatory responses. Understanding how bats control inflammatory response could help researchers find a way to limit human inflammation. Some underpinnings of this have been explored, but there is much left to be understood. Another way bat immunity may work is through continued expression of certain immune genes (keeping them in the “on” position) that may help them respond to infection faster.
RNA vs. DNA Viruses
Viruses come in one of two “brands,” DNA or RNA. DNA contains an organism’s genetic code (yours, too). RNA is like DNA, but typically acts as a messenger, transmitting instructions encoded by DNA to produce proteins. In RNA viruses like COVID-19, it is the RNA alone that carries the genetic code. These viruses can inject RNA into the cells of their host and directly create new viral proteins. The immune responses I mentioned earlier apply to RNA viruses, but bat responses to DNA viruses (like herpesvirus) are less understood (there is some neat information about DNA viruses in the reference paper, though).
I hope I have given you food for thought about why bat immunity matters. There is, however, another reason I wanted to call this to your attention. Scientists do important studies on lots of organisms, but it is not always clear to everyone how those studies relate to us, or why people should care about issues like how bats keep from getting sick. There is a surprising amount of genetic similarity between humans and other organisms (like bats, mice, and even fruit flies). Because of this, some organisms make great model systems through which to learn about humans. Next time you hear about a researcher studying mice or fruit flies, I hope you will not laugh it off as if someone is obsessed with a specific organism that you do not care much about. Instead, I hope you will remember the important role those organisms (and research concerning them) can play in helping us understand human health.